Libyan Prime Minister Ali Zeidan has threatened to use force against guards who have been protesting at some of the country's main oil ports for several weeks.

In a news conference on Thursday, the prime minister accused the guards of trying to sell oil outside official channels.

Zeidan said the leader of the protesters, Ibrahim al-Jathran, who is the regional head of the Petroleum Facilities Guard, wanted to sell the oil independently of Libya's state National Oil Corp.

“The head of the protesters wants to export oil for their own group, they do not want to make concessions,” he said.

“If any tanker comes to the port to pick up oil then we will use any means to stop it. This could involve the army, navy or air force.”

If any tanker comes to the port to pick up oil then we will use any means to stop it

Ali Zeidan , Prime Minister

In a critical challenge to the government, strikes at Libya's two largest ports have pushed production and exports, the lifeblood of the north African country's economy, to their lowest levels since the civil war that ousted veteran leader Muammar Gaddafi in 2011.

Oil Minister Abdelbari al-Arusi said all ports were shut except for Zawiya in the west.

"Libya has lost $1.6bn in oil sales since July 25 until today," al-Arusi said.

Earlier on Thursday his deputy, Omar Shakmak, said that negotiations to resume exports from Es Sider, the country's biggest crude oil terminal, had failed.

No comment was immediately available from the protesters, who have not publicly threatened to sell oil independently.

The protests are located mainly in the eastern portion of Libya.

At the major sites, Es Sider and Ras Lanuf, the strikes began with armed security guards asking for higher pay.

The two ports have a combined export capacity of just less than 600,000 barrels per day, out of Libya's total of just over 1.2 million barrels per day.

The outages have been a major factor in pushing up world oil prices, with benchmark Brent futures hitting a four-month high of around $111 a barrel on Thursday.

Source: Agencies