Libya's army told former militia fighters and protesters to end their occupations of oilfields and ports and allow crude exports to restart, saying the OPEC country risked sliding into lawlessness.

Prime Minister Ali Zeidan has so far failed to negotiate an end to a series of sit-ins and strikes by security guards, civil servants, militiamen and other groups calling for everything from security and autonomy to a greater share of oil wealth.

Two years after the NATO-led uprising ousted Muammar Gaddafi, Libya's new military has struggled to control militias who helped topple Gaddafi and also continue to fight over territory and political feuds.

Analysts estimate months of shutdowns at port and oilfields have caused an estimated $6 billion in losses.

The army did not say what it would do if its warning was not heeded.

"End your strikes without condition so the oil flows to the ports and the economy recovers so we can build up the state and the armed forces," the chief of army staff said in a statement posted on the defense ministry's website late on Saturday.

"Our country is threatened by disintegration and lawlessness," it said.

The army repeated Zeidan's warnings that militias who did not join the regular armed forces by Dec 15 would be removed from the government payroll.

Many of the former fighters have been put on government pay in an attempt to co-opt them. But most remain loyal to their tribal or regional commanders.

The prime minister appears to be counting on rising popular anger against the militias since clashes in Tripoli killed more than 40 people this month and forced several powerful militia groups to withdraw from the capital.

He has warned the government will not be able to pay civil servants if ports strikes continue.

Last week, Libya's oil workers union also asked an autonomy movement leader to reopen the eastern Ras Lanuf oil port, Libya's second-biggest which used to export more than 200,000 barrels a day.

Analysts estimate oil exports are down to a fifth of the more than 1 million barrels per day Libya used to export until the summer, when the protests began.