Libya's new Prime Minister Ahmed Maiteeq won a vote of confidence from parliament on Sunday in defiance of a renegade former army general who has challenged the assembly's legitimacy.

Maiteeq, backed by the Muslim Brotherhood, was initially elected two weeks ago after a chaotic parliamentary session that some lawmakers had rejected as illegal.

Libya's legislature is at the centre of a growing standoff between rogue former general, Khalifa Haftar, with a loose alliance of anti-Islamist militias, and pro-Islamist factions positioning for influence in the North African country.

The Europe Union's special envoy on Sunday called the crisis Libya's worst since the 2011 war ousted Muammar Gaddafi, with the fragile government struggling to control brigades of former rebels and militias who are now key powerbrokers.

Lawmakers met on Sunday under heavy security to vote to approve Maiteeq's government, a week after militia forces claiming loyalty to Haftar attacked the congress to demand lawmakers hand over power.

"The congress has granted Prime Minister Ahmed Maiteeq its confidence. Out of 95 members, 83 voted in favour of his government," Abdulhamid Ismail Yarbu, an independent lawmaker told Reuters.

Another lawmaker confirmed the votes for Maiteeq, a businessman who will be Libya's third premier since March after months of unrest in the Opec oil producer.

There was no immediate response from a spokesman to Haftar, a former Gaddafi ally who broke with the Libyan autocrat in the 1980s, sought exile in the United States and returned to help fight in the 2011 war to end his one-man rule.

Three years after a Nato-backed revolt toppled Gaddafi, Libya still has no national army, no new constitution and its parliament is caught up in infighting that has delayed the country's transition to full democracy.

Powerful rival brigades of former rebel fighters, still heavily armed with anti-aircraft cannons and armoured vehicles, often make demands on the weak state. Each is loosely allied with competing Islamist and anti-Islamist political forces squaring off for control.

In March, the parliament ousted one premier, and his successor also asked to step down after his family was attacked by gunmen. - Reuters