Gunmen stormed Libya’s state oil firm in the capital Tripoli on Monday, killing at least two people and wounding 10, according to the Health Ministry.

“The initial toll of an explosion that targeted the headquarters of the National Oil Corporation was two dead and 10 wounded,” the ministry said on its Facebook page.

No group has claimed responsibility for the attack. It comes just days after a UN-brokered ceasefire was declared in Tripoli following a month of deadly street fighting. The violence left 61 people dead and allowed hundreds of convicts to escape from prison.

Oil is critical to Libya’s economy, accounting for more than 82% of its export earnings, according to OPEC.