Forces loyal to Muammar Gaddafi defending the coastal city of Sirte are facing a fierce bombardment by rebel troops guardian.co.uk

Forces of Libya's new government have launched their largest assault so far on the coastal city of Sirte in the hope of taking the last major Gaddafi stronghold by the end of the week.

After a massive dawn barrage of artillery and rockets, hundreds of fighters attempted to enter the city in columns of vehicles, appearing to gain some ground in early fighting.

Columns of smoke were visible across the skyline of Sirte with the sound of heavy fighting continuing throughout the morning.

In a sign of the intensity of the resistance by those inside the city, a constant stream of ambulances was seen taking the wounded from the battle towards a field hospital outside Sirte.

Also leaving in larger numbers than in recent days were civilians who had managed to flee the surrounded city.

At one frontline position, a farm building on the outskirts held until Thursday by Gaddafi fighters, fires were visible from across the fields.

Marksmen inside the building traded fire with Gaddafi snipers in the city.

The long-drawn-out battle for Sirte has been marked by frequent reversals of fortune for the besieging forces who are under intense pressure to capture the city. Its fall, the interim government has announced, will mark the "full liberation of Libya" and the beginning of a political process for elections in eight months.

Earlier in the week, fighting focused on a collection of buildings near the Ibn Sana hospital which became the target of the tanks, rocket launchers and anti-aircraft guns of Libya's revolutionaries lined up on the low sandy ridge that overlooks Sirte.

On Thursday a pall of white smoke hung across this district as shells exploded every few minutes, and people in a hotel warned of a sniper firing from the minaret of a mosque 500 metres away.

"We want to get this thing finished quickly," said a young bearded fighter standing by the wrecked lifts. "We had a plan to try to open the road to the hospital to evacuate civilians, but there were too many snipers. Yesterday we tried many times to open the road."

The battle for Sirte has come at a high cost for civilians. They are trapped, with dwindling supplies of food and water and no proper medical facilities to treat the wounded. Many residents are members of Gaddafi's own tribe and those fleeing the city blamed the death and destruction on the forces of the new government, and Nato, whose warplanes have been flying sorties overhead.

Hajj Abdullah, in his late 50s, was at a Red Cross post on the edge of Sirte where food was being handed out, explaining he had just escaped the city. "My 11-year-old died from the Nato rockets … I buried him where he died because it was too dangerous to go to the cemetery," he told Reuters. "There are random strikes in the city. People are dying in their houses."

There is no water, electricity or petrol. People who come out of Sirte – including deserters – say everything is very expensive. Even a cigarette lighter costs four dollars.

"When we see deserters, sometimes they try to come out with their families, but we find a pistol or papers saying who they are. They know it is finished. The last deserter that we had was a week ago from Gaddafi's tribe," said a fighter.