Top Republican US Senator John McCain said on Wednesday that war-ravaged Libya faced several challenges, including the need to stop human rights abuses, but also praised the country's progress.

"We are very happy to be back here in Libya and to note the enormous progress and changes made in the past few months," McCain, who was accompanied by four other US senators, said at a press conference in Tripoli.

The delegation met with Libyan officials, including National Transitional Council head Mustafa Abdel Jalil, the head of Tripoli military council, Abdelhakim Belhaj, and representatives of the Misrata military council.

McCain, an early ally of the now ruling NTC, said the purpose of the visit was to "see first hand the progress that has been made and how the United States can best assist during this period of transition."

Central to the talks was the reintegration of rebels into the national army, the securing of borders, planning for the upcoming election in June and providing better treatment for the war wounded.

"We know that many challenges lie ahead... but we are encouraged by what we have seen," he said.

McCain said that one of those challenges -- stamping out human rights abuses -- was raised in talks with representatives of the powerful Misrata military council, which oversees 250 militias, according to Human Rights Watch.

The watchdog on Wednesday called on Misrata authorities to order the militias under their control to stop the looting and destruction of homes, and to deploy a protective force to facilitate the return of displaced people.

Misrata officials accuse the displaced people of Tomina, Kararim, and Tawarga of having fought alongside Kadhafi's forces in committing atrocities against Misratans during the 2011 conflict, according to HRW.

"We made it clear to them that human rights organisations are reporting serious abuses and the world is watching," McCain said, adding that the senators would visit a Tawarga refugee camp later in the day.

"We know it is difficult but these abuses really need to be stopped so that Libya can be respected in every way throughout the world," he stressed.

The four senators accompanying McCain were Republicans Lindsey Graham, John Hoeven and Jeff Sessions, and Democrat Richard Blumenthal.