Libya’s ousted prime minister fled to Europe after the parliament voted him out, leaving behind a country at risk of being torn apart as tensions between its eastern and western regions broke open Wednesday.

A western-based militia fighting in the name of the parliament has launched an offensive against an autonomy-minded militia in the east that for months has occupied most of Libya’s crucial oil facilities, seizing virtual control of the country’s most vital resource and its almost sole source of cash.

This past week, the eastern militia succeeded in exporting a tanker of oil from a port it holds, in defiance of the central government.

In response to the offensive, other eastern militias are fighting back. Eastern leaders have warned that unless Tripoli backs down, they will seek outright independence for their region rather than greater autonomy.

Since the 2011 civil war that ousted longtime strongman Moammar Gaddafi, Libya has been torn among rival, heavily armed militias affiliated to regions, cities and tribes, while the central government, which inherited a Gaddafi-era military and police force that was in disarray, has been unable to exert its authority.

The militias have also lined up on rival sides of a political struggle between Islamist politicians and their opponents.

The success of the Islamist-leaning parliament in voting out the secular Ali Zeidan as prime minister Tuesday has sparked fears among its opponents of a power grab by the Islamists, which could translate into militia clashes. After the vote, Islamist-allied militias demanded that rival militias leave the capital. Instead, some anti-Islamist militias beefed up their positions in the city with armored vehicles mounted with heavy machine guns and antiaircraft guns.