TRIPOLI, Libya — Col. Muammar el-Qaddafi’s four-decade-old grip on power dissolved with astonishing speed on Monday as rebels marched into the capital and arrested two of his sons, while residents raucously celebrated the prospective end of his four-decade-old rule. Colonel Qaddafi’s precise whereabouts remained unknown.
In the city’s central Green Square, the site of many manufactured rallies in support of Colonel Qaddafi, jubilant Libyans tore down posters of him and stomped on them. The rebel leadership announced that the elite presidential guard protecting the Libyan leader had surrendered and that their forces controlled many parts of the city, but not Colonel Qaddafi’s leadership compound.
The National Transitional Council, the rebel governing body, issued a mass text message saying: “We congratulate the Libyan people for the fall of Muammar Qaddafi and call on the Libyan people to go into the street to protect the public property. Long live free Libya.”
Officials loyal to Colonel Qaddafi insisted that the fight was not over, and there were clashes between rebels and government troops early on Monday morning. Explosions and the sound of mortars could still be heard Monday morning and a rebel fighter told Al Jazeera television that pro-Qaddafi forces still controlled 15 to 20 percent of the capital. News reports quoting rebel officials said tanks had emerged from Colonel Qaddafi’s compound and had opened fire.
NATO and American officials said that the Qaddafi government’s control of Tripoli, which had been its final stronghold, was now in doubt.
President Obama said Sunday night that Colonel Qaddafi and his inner circle had “to recognize that their rule has come to an end” and called on Colonel Qaddafi “to relinquish power once and for all.” He also called on the National Transitional Council to avoid civilian casualties and protect state institutions as it took control of the country.
“Tonight, the momentum against the Qaddafi regime has reached a tipping point,” Mr. Obama said in a statement. “Tripoli is slipping from the grasp of a tyrant. The Qaddafi regime is showing signs of collapsing. The people of Libya are showing that the universal pursuit of dignity and freedom is far stronger than the iron fist of a dictator.”
The shocking collapse of the Qaddafi forces appeared to signal the end for one of the world’s most flamboyant and mercurial political figures, the leader of an idiosyncratic government that was frequently as bizarre as it was brutal.
Long a thorn in the side of the West after he took power in a bloodless coup in 1969, Colonel Qaddafi had managed an awkward reconciliation in recent years, abandoning his fledgling nuclear program and paying billions of dollars to the victims of the Pan Am Flight 103 bombing, which was attributed to Libyan agents.
While denying that he actually headed the government, Colonel Qaddafi created a cult of personality that centered on his Green Book, a volume both trivial and impenetrable. His decades of iron-fisted rule have produced a country, analysts say, that is devoid of credible institutions and any semblance of a civil society — a potential source of trouble in the months and years ahead.
After six months of inconclusive fighting, the assault on the capital unfolded at a breakneck pace, with insurgents capturing a base of the vaunted Khamis Brigade, where they had expected to meet resistance, then speeding toward Tripoli and through several neighborhoods of the capital effectively unopposed.
A separate group of rebels waged a fierce battle near the Rixos Hotel, a bastion of Qaddafi support near the city center. A team of rebels there captured Colonel Qaddafi’s son and one-time heir apparent, Seif al-Islam. Rebels also claimed to have accepted the surrender of a second Qaddafi son, Mohammed.
Rebel spokesmen said that their fighters had surrounded the Bab al-Aziziya compound where they believed Colonel Qaddafi might still be holding out, but that they were reluctant to begin an all-out assault. Colonel Qaddafi issued a series of defiant audio statements during the night, calling on people to “save Tripoli” from a rebel offensive. He said Libyans were becoming “slaves of the imperialists” and that “all the tribes are now marching on Tripoli.”
Mahmoud Hamza, a senior official of the Qaddafi Foreign Ministry, acknowledged in a phone call at 1 a.m. local time on Monday that “it is getting near the end now.” But he said that the Qaddafi forces had not given up.
“Tripoli now is very dangerous. There is a lot of fighting, but there is not yet an assault on Bab al-Aziziya,” he said. “For me this is the most fearful thing. I hope it does not come to that.”
Al Arabiya television broadcast images of Libyans celebrating in central Tripoli and ripping down Qaddafi posters. Huge crowds gathered in Benghazi, the capital of the rebel-controlled eastern part of the country, as expectations grew that Colonel Qaddafi’s hold on power was crumbling.
Earlier on Sunday, protesters took to the streets, and cells of rebels inside Tripoli clashed with Qaddafi loyalists, opposition leaders and refugees from the city said. Fighting had been heavy in the morning, but by midnight Colonel Qaddafi’s forces had withdrawn from many districts without a major battle.
A rebel spokesman said insurgents had opened another line of attack on Tripoli by sending boats from the port city of Misurata to link up with fighters in the capital. It was not clear how many fighters were involved in that operation.
Moussa Ibrahim, the government’s spokesman, issued press statements through the night, saying that more than 1,300 people had died in fighting in the city, but that government troops remained in control. Those claims could not be confirmed.
But the turmoil inside Tripoli and the crumbling of defenses on its outskirts suggested a decisive shift in the revolt, the most violent of the Arab Spring uprisings.
NATO troops continued close air support of the rebels all day, with multiple strikes by alliance aircraft helping clear the road to Tripoli from Zawiyah. Rebel leaders in the west credited NATO with thwarting an attempt on Sunday by Qaddafi loyalists to reclaim Zawiyah with a flank assault on the city.
Seif al-Islam el-Qaddafi has been a central character in the drama of the revolt. Before the uprising began he was known as Libya’s leading advocate of reform in both economic and political life. He cultivated an Anglophile persona, and often appeared to be waging a tug of war against his father’s older and more conservative allies. He was increasingly seen as the most powerful figure behind the scenes of the government as well as his father’s likely successor.
When the revolt broke out it was Seif al-Islam who delivered the government’s first public response, vowing to wipe out what he called “the rats” and warning of a civil war.
In his last public interview, he appeared a changed man. Sitting in a spare hotel conference room, he wore a newly grown beard and fingered prayer beads. After months of denouncing the rebels as dangerous Islamic radicals, he said that he was brokering a new alliance with the Islamist faction among the rebels to drive out the liberals.
While rebels expressed hope that Colonel Qaddafi’s forces had lost their will to fight, support for the government could remain strong inside areas of Tripoli. Analysts said the crucial role played by NATO in aiding the rebel advance in the relatively unpopulated areas outside the capital could prove far less effective in an urban setting, where concerns about civilian casualties could hamper the alliance’s ability to focus on government troops.
A senior American military officer who has been following the developments closely, and who has been in contact with African and Arab military leaders in recent days, expressed caution on Sunday about the prospects for Libya even if the Qaddafi government should fall. Even if Colonel Qaddafi is deposed in some way, the senior officer said, there was still no clear plan for a political succession or for maintaining security in the country.
“The leaders I’ve talked to do not have a clear understanding how this will all play out,” said the officer, who spoke on condition of anonymity because he was not authorized to discuss the issue publicly.
Few would have predicted that the rebels would meet so little resistance from the 32nd Brigade, a unit that NATO had considered one of the most elite in Libya and commanded by Khamis Qaddafi, one of the leader’s sons. The so-called Khamis Brigade was one of the crucial units enforcing the defense lines around the capital, extending about 17 miles outside Tripoli to the west and about 20 miles to the south.
Rebels said those points had been breached by Sunday afternoon despite the expectation that Colonel Qaddafi would use armored units and artillery to defend them. It was unclear whether the government troops had staged a tactical retreat or had been dislodged by NATO strikes.
After a brief gun battle, rebels took over one of the brigade’s bases along the road to Tripoli. Inside the base, rebels raised their flag and cheered wildly. They began carting away stores of weapons, including rocket-propelled grenades and mortars.
While the bodies of several dead loyalist soldiers were left on the ground in the base, it appeared the troops there had retreated rather than being forced out in battle. At least one structure suffered significant damage from NATO bombs.
American officials say they are preparing contingency plans if and when Colonel Qaddafi’s government falls to help prevent the vast Libyan government stockpiles of weapons, particularly portable antiaircraft missiles, from being stolen and dispersed.
Untold numbers of the missiles, including SA-7s, have already been looted from government arsenals, and American officials fear they could circulate widely, including heat-seeking antiaircraft missiles that could be used against civilian airliners. The senior military officer said the United States had already been quietly meeting with leaders of Libya’s neighbors to stem the flow of the missiles and could send small teams of American military and other government weapons experts into Libya after the fall of the Qaddafi government to help Libyan rebel and other international forces secure the weapons.
Early Monday, the Human Rights Watch advocacy group urged the combatants to “do everything feasible to protect civilians caught in the fighting” and said rebels “should not carry out reprisals against those who fought for or supported” Colonel Qaddafi’s regime.