DUBAI, United Arab Emirates — Southern Yemeni separatists withdrew on Saturday from some government buildings in Aden that they seized last week but held on to military camps that give them control over the city, which is Yemen’s southern port and the interim seat of Yemen’s ousted Saudi-backed government.

The separatists’ takeover of Aden has strained a Saudi-led military coalition formed to confront the Iranian-aligned Houthis, who bombed a Saudi oil facility on Saturday.

A Houthi military spokesman said 10 drones launched toward oil installations at Shaybah in eastern Saudi Arabia constituted the “biggest attack in the depths” of the kingdom.

The state oil company Saudi Aramco said the attack had caused a “limited fire” at a gas plant which had been contained and had not affected production. Energy Minister Khalid al-Falih condemned the strike as “cowardly” sabotage.