Libya’s government will use all means, including military force, to prevent striking security guards at the country’s main ports from selling its oil independently, Prime Minister Ali Zeidan said late on Thursday.

In a critical challenge to the government, strikes at Libya’s largest ports have pushed oil 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.

Libyan supply disruptions have helped push oil prices to their highest levels since April alongside unrest in neighbouring Egypt where hundreds were killed in clashes between security forces and protesters this week.

Libyan officials said patience with protesters was running out as the country was losing billions and its oil exports more than halved in the past weeks.

Prime Minister Zeidan said that the leader of the protesters, Ibrahim al-Jathran, the regional head of the Petroleum Facilities Guard, wanted to sell the oil independently of Libya’s state national oil corporation (NOC).

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

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

The protests are located mainly in the eastern part of Libya, which has been pushing for greater autonomy since starting the uprising against Gaddafi.

The strikes have hit major oil export sites such as Es Sider and Ras Lanuf, with armed security guards asking for higher pay.

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