Libyan leader Moammar Gadhafi has urged his supporters to rise up and defeat the rebels trying to oust him from power.

In a short audio broadcast on Thursday, he described his opponents as “rats” and also denounced foreign countries for their involvement in the conflict.

His speech came as fierce gunbattles between pro-Gadafi forces and opposition fighters erupted in at least two areas of the capital, Tripoli.

Heavy fighting broke in the Abu Salim neighborhood, a pro-Gadhafi stronghold. Rebels have been conducting raids in the neighborhood in search of Gadhafi loyalists. Earlier Thursday, witnesses reported hearing a barrage of gunfire outside of the Corinthia hotel, where many foreign journalists are staying.

Opposition fighters have been pouring into Tripoli to help combat the remnants of pro-Gadhafi resistance. They are also advancing toward Mr. Gadhafi's hometown of Sirte.

Pro-Gadhafi forces have been massing for a showdown in Sirte, which is about 400 kilometers east of Tripoli.

Mr. Gadhafi's whereabouts are unknown, but U.S. officials believe he is still in Libya. Also, the Associated Press has quoted a Gadhafi spokesman as saying Thursday that the Libyan leader is “safe,” “healthy” and leading the fight against rebels.

Britain says NATO is helping rebels in their hunt for Mr. Gadhafi and members of his regime. British Defense Minister Liam Fox told Britain's Sky News on Thursday that NATO is providing the rebels with intelligence and reconnaissance equipment to aid in their search. However, NATO spokeswoman Oana Lungescu says the alliance does not target individuals.

The U.S. State Department said Thursday it believes Libya's stockpiles of mustard gas and a low-enriched uranium called yellowcake are safe. However, spokeswoman Victoria Nuland says shoulder-fired missiles known as “MANPADS” remain a concern.

In rebel-held Benghazi, the Transitional National Council's Mustafa Abdel Jalil urged Libyans in parts of the country that were still under the the control of Gadhafi forces to join the “revolution.”

Also Thursday, foreign correspondents in Tripoli viewed the bodies of at least 15 men who appeared to have been executed. It was not clear who killed them.

In another development, a TNC leader called Thursday for “urgent” financial help. Mahmoud Jibril said the money is needed to pay the salaries of Libyans and deliver basic services to civilians.

He made the plea during a news conference in Milan with Italian Prime Minister Silvio Berlusconi, who said his country was ready to unfreeze up to $505 million in Libyan assets.

The TNC has begun moving some of its ministries from rebel-held Benghazi to Tripoli. The group's leaders say that elections will be held in eight months.

On Wednesday, the TNC said it supports a decision by Libyan businessmen to provide a $1.67 million reward in an attempt to speed up Mr. Gadhafi's capture.

Meanwhile, the International Organization for Migration says it has begun evacuating foreigners who want to leave Tripoli. The international relief group said Thursday that about 200 people had begun boarding a ship docked near the capital. Concerns about the security situation in the city had kept the vessel off shore for days.