Libyan provisional government forces, backed by NATO, launched an assault on one of the last remaining strongholds of ousted leader Moammar Gadhafi Saturday.

The fighters encountered stiff resistance from Gadhafi loyalists in the desert town of Bani Walid, a day after they pushed into the town.

But despite the continued fighting, authority forces expressed confidence that they were close to victory. They said they were going door-to-door looking for snipers and other Gadhafi loyalists, while NATO jets provided air support.

A VOA correspondent ) near Bani Walid said heavy artillery fire could be heard from the scene.

The National Transitional Council said its fighters moved on Bani Walid Friday, after loyalists fired a barrage of rockets at NTC positions. Al Jazeera Television reported heavy fighting in other towns, including Sabha and Mr. Gadhafi's hometown of Sirte.

Provisional authorities had given three main Gadhafi-held towns until Saturday to surrender. But an NTC spokesman said it was still not too late for Gadhafi loyalists to give up.

Also Saturday, NTC leader Mustafa Abdel Jalil arrived in Tripoli for the first time since his group took over the capital in August. The NTC has announced plans to move its headquarters from the eastern city of Benghazi to Tripoli.

Meanwhile, the International Monetary Fund has recognized the NTC as Libya's official government.

The group announced its decision at a Saturday meeting in France, where international financial institutions promised an additional $38 billion for four Arab countries trying to transition to democracy.

On Friday, Interpol issued an arrest warrant for Mr. Gadhafi, his son Saif al-Islam and Libya's former intelligence chief, Abdullah al-Senussi.