Moammar Gaddafi-backed forces have reportedly launched fresh air strikes on the key oil port city of Ras Lanuf, raising fears about the vulnerability of local gas facilities and a possible humanitarian catastrophe.

Al Jazeera reported that Libyan government fighter jets were flying above the Ras Lanuf petroleum facilities, but that rebels were firing back.

What we are hearing is intense and repeated attacks by Gaddafi's airplanes on the rebels, a reporter in the city told Al Jazeera.

The air force is concentrating on the big junctions at the entrance to the town. The fact that it’s such consistent black smoke could well means there is oil underneath it. It is continuing to burn. The opposition fighters are extremely panicked.

According to an opposition member in Ras Lanuf, Khaled Kwafi, some people were killed and injured in the air raid.

An hour ago we saw warplanes in the sky. We heard very huge explosions and lots of smoke. Our people tried to go there but they were stopped, he said. We heard there are people killed and injured there.

The Ras Lanuf refinery, Libya’s largest crude-processing plant, was shut down amidst the fighting, a representative of Libyan Emirates Oil Refining Co. said.

There is much concern now about what Gaddafi will do next to secure his oil needs.

“We expect that he will destroy everything because he is crazy, Fahad Kheri, superintendent in Libya's oil and gas Industry, told Al Jazeera.

“With the violence escalating, it was a question of time when oil facilities would be drawn into the fighting,” Samuel Ciszuk, senior Middle East energy analyst at IHS Global Insight in London, told Bloomberg.

“To dislodge opposition forces, you need to take these facilities. That would entail hitting some.”

Forces loyal to Gaddafi have reportedly also bombarded rebel positions in Es Sider, an oil terminal in eastern Libya, destroying storage tanks there. Rebels fought back with rockets.

In addition, Gaddafi troops are also reportedly encroaching upon the town of Aw Zawiyah one of the few areas in the western part of the country currently on rebel hands. There were reports of many dead bodies and destroyed buildings in the town, which is near Tripoli.

We can see the tanks. The tanks are everywhere, a rebel fighter in Zawiyah told Reuters.

Meanwhile, unconfirmed and conflicting reports indicate that Gaddafi may have sent an envoy to rebel groups to discuss a possible negotiated exit for Gaddafi and his family. However, Libyan state TV has denied then reports.