Libya's parliament moved to a luxury hotel on Tuesday until a powerful militia from the western city of Misrata can take up positions to protect its old building, which was attacked by gunmen on Sunday, a parliamentary spokesman said.

Gunmen shelled the General National Congress on Sunday in an attack claimed by forces loyal to renegade general Khalifa Haftar, who said it was part of a campaign to purge the North African country of Islamists.

Haftar's troops on Friday attacked Islamist militants in Benghazi in the worst clashes in the eastern city for months, killing more than 70 people.

Western powers fear Haftar's campaign will split the Libyan army, further destabilising the country, after several units defected to him in recent days.

Calm has returned to Tripoli since Sunday but diplomats say the involvement of a militia from Misrata might create new tensions.

The Islamist Muslim Brothers have strong roots in Misrata and are rivals of a militia from Zintan in the western mountains, which controls part of Tripoli and which some officials have blamed for the attack on the parliament.

The struggle takes place against a background of growing chaos in Libya, where the government is unable to control dozens of militias who helped oust Muammar Gaddafi in 2011 but now defy state authority.

Parliamentary spokesman Omar Hmeidan said speaker Nuri Abu Sahmain had asked the force from Misrata to secure parliament's premises.

"The Congress decided to hold today's session in a hall of the Radisson Blu hotel until the Central Shield force from Misrata finishes preparations to start securing the headquarters of the Congress," he said.

Parliament had planned to discuss approving a cabinet for newly appointed prime minister Ahmed Maiteeq, but postponed debate as it lacked a quorum, he said.

The appointment of Maiteeq, who is from Misrata, has angered people in the east since he is supported by the Muslim Brothers.

Outgoing premier Abdullah al-Thinni on Monday asked parliament to stop work and re-run the controversial election that brought Maiteeq to power, compounding the country's political crisis.

Hmeidan confirmed that a congressman, Masoud Abdulsalam Obaid, and two employees had been kidnapped by the gunmen who attacked the parliament on Sunday.-Reuters