Libyan government forces dropped bombs on four large oil storage tanks in the contested western city of Misrata, destroying the tanks and sparking a fire that spread to four more, a rebel spokesman said on Saturday.

Government forces used small planes normally used to spray pesticides for the overnight attack in Qasr Ahmed close to the port, rebel spokesman Ahmed Hassan told Reuters.

"Four tanks were totally destroyed and huge fire erupted which spread now to the other four. We cannot extinguish it because we do not have the right tools," he said.

"Now the city will face a major problem. Those were the only source of fuel for the city. These tanks could have kept the city for three months with enough fuel," he said by telephone.

Rebels notified Nato about the planes before the attack but there was no response, he said. Government forces last month flew at least one helicopter reconnaisance mission over Misrata, according to rebels.

Misrata is the last remaining city in the east under rebel control. It has been under seige for more than two months and has witnessed some of the war's fiercest fighting between loyalists and rebels. – Reuters