Forces loyal to Moammar Gadhafi battled rebels in scattered pockets of the Libyan capital late Monday, as the country's leader continued to elude capture.

The head of the opposition Transitional National Council, Mustafa Abdel Jalil, said the rebels do not know whether Mr. Gadhafi is still in the country. He said the Libyan leader will receive a fair trial once captured and that the “real moment of victory” will be when he is taken into custody.

Jalil acknowledged that the rebels have yet to establish full control in Tripoli. Opposition fighters say pro-government forces still hold 10-15 percent of the capital, including Mr. Gadhafi's Bab al-Aziziya compound.

Fighting had intensified earlier Monday when tanks emerged from the compound and opened fire, although months of NATO airstirkes have left the area largely demolished.

Officials close to the Libyan leader say he will not go easily, even after the rebels announced they had arrested three of Mr. Gadhafi's seven sons, including his one-time heir apparent, Seif al-Islam. However, senior rebel sources said later that one of the sons – Mohammed – had escaped house arrest.

Meanwhile, Libyan state television remained off the air late Monday amid reports that rebels seized what had become a key instrument of government propaganda.

The rebels broke through Tripoli's outer defenses Sunday and reached the city's central Green Square, where thousands celebrated the opposition's arrival.

Jubilant Libyans in the square, which the rebels have renamed Martyrs Square, tore down posters of Mr. Gadhafi and stomped on them. Until recently, the government had used the area for mass demonstrations in support of Mr. Gadhafi.

The rebel troops moved into central Tripoli with little resistance after capturing a key military base run by the government's elite Khamis Brigade and commanded by another of Mr. Gadhafi's sons as they advanced from the west. On their way into the capital, opposition forces also freed several hundred prisoners from a government jail.

International Criminal Court prosecutor Luis Moreno-Ocampo said Monday he will contact the rebels and urge them to surrender Seif al-Islam to the Hague-based court as soon as possible. Seif al-Islam is indicted along with his father and Libya's intelligence chief on charges of crimes against humanity for allegedly planning and ordering attacks on civilians in the early days of the crackdown on anti-government protests.

The International Organization for Migration said it had chartered a boat to Tripoli to begin evacuating stranded migrants. The boat, which can carry 300 people, left Benghazi early Monday.

Huge crowds gathered early Monday on the streets of Benghazi, the rebel capital in eastern Libya, as reports of the assault on Tripoli grew and expectations mounted that Mr. Gadhafi's hold on power was faltering.

On Sunday, Libyan state television broadcast a series of defiant audio messages from Mr. Gadhafi. In one, he acknowledged that opposition forces were moving into Tripoli. The Libyan leader said he would stay in the capital “until the end” to defend the city and called on supporters to help liberate it.

The Libyan leader has seen the areas under his control shrink significantly in recent weeks as rebels advanced on Tripoli from the west, east and south after six months of fighting to end his four-decade rule.

NATO warplanes have been supporting the rebels by bombing pro-Gadhafi forces under a U.N. Security Council resolution authorizing military action to protect Libyan civilians from government attacks.