Tripoli alert as rebels close in

Libyan rebels have launched an assault on Zawiya's oil refinery to drive the last of Colonel Muammar Gaddafi's forces from the city west of Tripoli and tighten their noose around the capital.

Col Gaddafi, 69, seems increasingly isolated, with rebels now closing in from west, south and east on his stronghold on the Mediterranean coast.

His forces had held Zawiya, which produces 120,000 barrels of oil a day and controls the road to Tripoli, and have been harassing rebels in the city with shelling and sniper fire.

Rebel fighter Abdulkarim Kashaba said: "There are some snipers inside the refinery facility. We control the gates of the refinery. We will be launching an operation to try to take control of it shortly."

Remaining Gaddafi loyalists have closed the gate of the residential compound for refinery workers and their families but many of the workers were evacuated early in the civil war that began in mid-February.

"If (the civilians] leave, we can deal with Gaddafi's guys with full force," said Osama Arus, a rebel field commander in Zawiya. "So Gaddafi's guys don't want them to leave. They keep them as protection."

Aided by Nato's fighter-bombers, assault helicopters and naval blockade, the rebels have transformed the battle in the past few days after many weeks of stalemate. RAF Tornado GR4 aircraft, normally based at Lossiemouth, flew from RAF Marham in Norfolk on Wednesday night to attack targets in Libya with Storm Shadow cruise missiles, Ministry of Defence sources said. The mission took around eight hours.

A rebel spokesman from the rebel-held city of Misrata to the east of Tripoli said they had found the bodies of civilians slaughtered by Gaddafi forces.

He said: "We discovered a mass grave containing 150 bodies in Tawargha. These are the corpses of civilians kidnapped from Misrata by Gaddafi's loyalists." Rebels found a video "showing kidnappers cutting the throats of people", he added.

The spokesman said rebel forces were now outside a place called Hisha about 60 miles west of Misrata on the road to Tripoli. "They are now on the coastal road," he said.

Gaddafi's green flags were still flying from a refinery building and an electrical pylon last night. The rest of the city now flies the red, black and green flag of the rebels.

Streets were largely deserted apart from clusters of fighters and shops were shuttered. Medical workers said three people were killed and 35 injured on Tuesday, mostly civilians.

If the pipeline to Tripoli is cut, "that would imply dire consequences for the population in Tripoli in terms of fuel supplies", said Fernando Calado of the International Organisation for Migration. Mr Calado said there had been a sharp increase in the past week in the number of foreign nationals asking to be evacuated. He estimated more than 300,000 foreigners remain in Tripoli, including many from the Philippines, Sri Lanka, Chad, Egypt and Tunisia.

The flow of crude to the Zawiya refinery from fields in the south-west of Libya had largely been halted since mid-summer and the refinery was believed to be running at about one-third of capacity, drawing mainly on crude oil in its storage tanks. It was mainly producing heavy fuel oil, rather than petrol, which Gaddafi has been importing from Tunisia and Algeria.

"In that sense, it's more significant that they (the rebels] have got control of the roads than the refinery," said John Hamilton, a contributing editor of Africa Energy. "That's a more important gain. Having control of the roads makes it much harder for Gaddafi to get the petrol he needs" from Tunisia and Algeria.

Libya's rebel National Transitional Council (NTC) has denied holding secret talks with Gaddafi to end the war. But suspicions persist negotiation may be going on. The NTC, however, insists Gaddafi must leave Libya, saying talks ignoring this basic demand would be "unthinkable".