The crisis arose when protesters who have seized three eastern ports since August loaded crude onto a North Korean-flagged tanker at Es Sider terminal at the weekend.

The tanker left Es Sider on Tuesday. According to varying accounts by government officials, the navy or air force then fired on the vessel, although it was not clear if this happened in Libyan or international waters.

Government spokesman Habib al-Amin told a news conference in Tripoli that the firing failed to disable the tanker, which proceeded eastwards into Egyptian waters. He said Libya had asked Egypt and other countries to help stop the ship.

There was no independent confirmation of the tanker's whereabouts, destination or ownership.

The debacle underlines the impotence of the authorities in Tripoli, whose fledgling army and police force are no match for the militias and other armed groups who remain a law unto themselves three years after the fall of Muammar Gaddafi.

After the tanker escaped, an infuriated parliament voted out Zeidan on Tuesday and named Defense Minister Abdallah al-Thinni as acting prime minister for two weeks.

Officials said Libya was close to bankruptcy because of the six-month oil blockade, which cost the North African country an estimate $8 billion in lost revenue in 2013, and set a two-week deadline for talks with rebels to end the port seizures before force was used. Similar threats in the past have proved empty.

Libya's transitional assembly, the General National Council, said it would pick another replacement for Zeidan within two weeks before a parliamentary election expected later this year.

NJF/NJF