Of course, Gadhafi himself is still promising a fight:

Saif al-Islam Gadhafi, a son of Libya's ruler Moammar Gadhafi and a top official in the regime, has been captured by opposition forces, a rebel official said Sunday night.

Ali Said, general secretary of the Benghazi-based Transitional National Council, said that the arrest had taken place in Tripoli. The head of the same rebel group also confirmed the capture in an Al Jazeera interview. There was no immediate reaction from Libyan government officials to the report.

A day earlier, Saif al-Islam -- who had emerged as a leading spokesman for the regime since the unrest began in February -- had laughed off reports of rebels taking Tripoli and claimed that they were losing every battle.

But this account ran counter to reports from CNN reporters, witnesses and rebel officials on the ground. A NATO spokesman, in fact, said earlier Sunday that Moammar Gadhafi's "regime is crumbling."

But in an audio address broadcast Sunday on Libyan state television, the longtime Libyan ruler remained defiant in urging his countrymen to join him to stop "colonizers" and predicting an imminent "victory.

UPDATE: Per unconfirmed reports from the BBC, Gadhafi has escaped to Algeria.

More as it develops...