Libya’s parliament handed a no-confidence vote to Prime Minister Ali Zeidan on Tuesday in yet another jolt to the oil-rich nation’s crumbling political stability.

Libya’s elected General National Congress (GNC) ousted Zeidan a day after the government failed to stop a North Korean-flagged oil tanker from departing Libya’s eastern shore with an unauthorized $36 million cargo of crude oil.

Less than three years after the fall of dictator Moammar Gaddafi, Libya has been riven by increasingly violent political animosities as powerful militias, aligned with rival political factions, have struggled to exert control over key government offices, territory and — significantly — the country’s vast oil resources.

Federalist fighters seeking autonomy for eastern Libya have laid siege to some of the country’s key oil wells and ports, effectively paralyzing exports for the past six months.

The weekend docking of the North Korean tanker marked the first independent sale of oil by a non-state body, threatening to escalate regional and tribal tensions into a full-fledged war.

By Tuesday night, fighting had erupted in the central city of Sirte as militias, moving east from the city of Misurata in an effort to seize the eastern ports, came to blows with an eastern militia.

Zeidan had earlier threatened to use force if the tanker tried to leave. But after a three-day stand-off between the eastern rebels and government-allied forces, the rebels said Tuesday that the tanker had entered international waters.

“We don’t care what the GNC does with Zeidan. They can do what they like,” said Senussi El-Megrabi, a spokesman for rebel commander Ibrahim al-Jathran. “We have nothing to do with them.”

The tanker, the Morning Glory, left Libya’s Sidra port at 8 a.m., Megrabi said.

Libya’s deeply divided parliament on Tuesday designated the country’s defense minister to take over for Zeidan for the next 15 days until the body selects a new prime minister, state media reported. That person would become the country’s fifth prime minister in just over two years.

Zeidan’s popularity quickly plummeted during his year and a half in office, amid widespread frustration at his failure to empower the country’s weak government institutions and disarm the militias that control the streets. Zeidan’s opponents have accused him of having his own ties to one powerful militia and of making payoffs to others for their compliance.

The country appeared on the verge of spiraling into further chaos Tuesday night as rumors circulated in Tripoli that the tanker had come under attack and caught fire, and as the fighting raged on in Sirte.

Megrabi said that rebel forces had already repelled an earlier attack by Misurata fighters but were undeterred. The rebels have said that any attacks by government-allied forces would constitute an act of war.

“We are expecting another tanker to Heriga port,” he added. “But I don’t know when exactly that will be.”