TRIPOLI (AP) -- Euphoric Libyan rebels raced into the capital Tripoli on Sunday and moved close to center with little resistance as Moammar Gadhafi's defenses collapsed and his regime appeared to be crumbling fast.

Associated Press reporters with the rebels said they moved easily from the western outskirts into the regime stronghold in a dramatic turning of the tides in the 6-month-old Libyan civil war. A rebel leader said the unit in charge of protecting Gadhafi and Tripoli had surrendered and joined the revolt, allowing the opposition force to move in freely.

``They will enter Green Square tonight, God willing,'' said Mohammed al-Zawi, a 30-year-old rebel who entered Tripoli. Green Square has been the site of night rallies by Gadhafi supporters throughout the uprising.

Earlier in the day, the rebels overran a major military base defending the capital, carted away truckloads of weapons and raced to Tripoli with virtually no resistance.

Gadhafi's whereabouts were unknown. But he delivered a series of angry and defiant audio messages broadcast on state television. He was not shown in the messages. In the latest one, he acknowledged that the opposition forces were moving into Tripoli and warned the city would be turned into another Baghdad.

``How come you allow Tripoli the capital, to be under occupation once again?'' he said. ``The traitors are paving the way for the occupation forces to be deployed in Tripoli.''

He called on his supporters to march in the streets of the capital and ``purify it'' from ``the rats.''

Opposition leaders at one point claimed Gadhafi's son and one-time heir apparent, Seif al-Islam, had been arrested, but they later backtracked and said this was not yet confirmed.

The rebels' surprising and speedy leap forward, after six months of largely deadlocked civil war, was packed into just a few dramatic hours. By nightfall, they had advanced more than 20 miles to Tripoli.

Thousands of jubilant civilians rushed out of their homes to cheer the long convoys of pickup trucks packed with rebel fighters shooting in the air. Some of the fighters were hoarse, shouting: ``We are coming for you, frizz-head,'' a mocking nickname for Gadhafi. In villages along the way that fell to the rebels one after another, mosque loudspeakers blared ``Allahu Akbar,'' or ``God is great.''

``We are going to sacrifice our lives for freedom,'' said Nabil al-Ghowail, a 30-year-old dentist holding a rifle in the streets of Janzour, a suburb just six miles west of Tripoli. Heavy gunfire erupted nearby.

As town after town fell and Gadhafi forces disappeared, the mood turned euphoric. Some shouted: ``We are getting to Tripoli tonight.'' Others were shooting in the air, honking horns and yelling ``Allahu Akbar.''

Once they reached Tripoli, the rebels took control of one neighborhood, Ghot Shaal, on the western edge of the city. They set up checkpoints as a convoy of more than 10 trucks rolled in.

The rebels moved on to the neighborhood of Girgash, about a mile and a half from Green Square. They said they came under fire from a sniper on a rooftop in the neighborhood.

Sidiq al-Kibir, the rebel leadership council's representative for the capital Tripoli, confirmed the arrest of Seif al-Islam to the AP but did not give any further details.

Inside Tripoli, widespread clashes erupted for a second day between rebel ``sleeper cells'' and Gadhafi loyalists. Rebels fighter who spoke to relatives in Tripoli by phone said hundreds rushed into the streets in anti-regime protests in several neighborhoods.

The day's first breakthrough came when hundreds of rebels fought their way into a major symbol of the Gadhafi regime -- the base of the elite 32nd Brigade commanded by Gadhafi's son, Khamis. Fighters said they met with little resistance. They were 16 miles from the big prize, Tripoli.

Hundreds of rebels cheered wildly and danced as they took over the compound filled with eucalyptus trees, raising their tricolor from the front gate and tearing down a large billboard of Gadhafi.

Inside, they cracked open wooden crates labeled ``Libyan Armed Forces'' and loaded their trucks with huge quantities of munitions. One of the rebels carried off a tube of grenades, while another carted off two mortars.

``This is the wealth of the Libyan people that he was using against us,'' said Ahmed al-Ajdal, 27, pointing to his haul. ``Now we will use it against him and any other dictator who goes against the Libyan people.''

One group started up a tank, drove it out of the gate, crushing the median of the main highway and driving off toward Tripoli. Rebels celebrated the capture with deafening amounts of celebratory gunfire, filling the air with smoke.

Across the street, rebels raided a huge warehouse, making off with hundreds of crates of rockets, artillery shells and large-caliber ammunition. The warehouse had once been using to storage packaged foods, and in the back, cans of beans were still stacked toward the ceiling.

They freed several hundred prisoners from a regime lockup. The fighters and the prisoners -- many looking weak and dazed and showing scars and bruises from beatings -- embraced and wept with joy.

The prisoners had been held in the walled compound and when the rebels rushed in, they freed more than 300 of them.