Intense fighting is under way between Libya's provisional government fighters and former leader Moammar Gadhafi's holdouts for control of Mr. Gadhafi's hometown of Sirte.

National Transitional Council fighters say they have gained control of the airport in Sirte. However, clashes between the two sides continue in other parts of the city on Thursday.

Meanwhile, Libya's provisional government has gotten a show of support from visiting U.S. senators and a United Nations agency.

Four U.S. lawmakers traveled to Libya on Thursday in a trip that marked the first visit by U.S. congressmen to Tripoli since the fall of Mr. Gadhafi's government.

After the group met with NTC leaders, U.S. Senator John McCain urged the NTC to work to bring all of the country's armed groups under the control of the governing authority. He also urged provisional leaders to bring Mr. Gadhafi, his family members and his fighters to justice. Mr. Gadhafi remains at large as NTC forces hunt for him.

Another lawmaker, Senator Mark Kirk, said he would continue to lobby for the release of Libyan funds held in the U.S.

Separately, the U.N. Human Rights Council has recommended the lifting of Libya's membership suspension in the rights body. The council has adopted a resolution that calls for the U.N. General Assembly to lift the suspension that was imposed in March.

In another development, Interpol issued an international alert on Thursday to help find and arrest former Libyan leader Moammar Gadhafi's son, Saadi.

The international police agency says it issued a “red notice” at the request of provisional authorities in Libya, where a warrant has been issued for Saadi Gadhafi's arrest.

Interpol says he is wanted in Libya for allegedly misappropriating property and engaging in “armed intimidation” when he headed the Libyan Football Federation.

The agency says it has confirmed reports that Saadi Gadhafi was last seen in neighboring Niger. The alert seeks the help of countries in the region and those with travel links to Niger, with a view to returning him to Libya if he is arrested.

Interpol issued similar international alerts earlier this month for Mr. Gadhafi, his son Saif al-Islam and Libya's former intelligence chief.