Frontline closer to the capital than at any point since the uprising against Muammar Gaddafi's regime began

Libyan rebels are engaged in fierce fighting for control of the crucial town of Zawiya, west of Tripoli. Reporters accompanying the rebel advance on the town, which suffered a long siege from pro-Gaddafi forces, reported that a six-hour battle had pushed the frontline closer to the capital than at any point since the uprising against Muammar Gaddafi's regime began.

Eyewitnesses reported heavy clashes as a rebel force of about 200 fighters reached a bridge on the south-west outskirts of the city, located around 50km west of Tripoli. Some rebels pushed farther towards the city centre.

An Associated Press reporter travelling with the rebels saw hundreds of residents rush into the streets, greeting rebels with chants of "Allahu Akbar" (God is greatest).

The English language services of al-Arabiya and al-Jazeera claimed that rebels had advanced into the town itself, a claim also made by social media sources who said that rebels had reached the town centre.

The fighting around Zawiya comes as rebels also advanced through the Nafusa mountains, entering the town of Gharyan before being confronted by pro-Gaddafi troops.

The recapture of Zawiya, which became a potent symbol of the Libyan uprising, would be hugely significant. Half an hour's drive from the capital, Tripoli, and located on the western approach to the capital, it would threaten a key supply line for pro-Gaddafi forces. However, there are a number of significant military bases near to the town.

Rebel fighters pushed government troops back about 7km from their previous positions, fixing a frontline about 5km north of the village of Bir Shuaib.

Michael Georgy of Reuters, reported being told of a heavy battle, with pro-Gaddafi forces using anti-tank guns.

AP told a similar story quoting rebel commander Fathi el-Ayeb saying his fighters were about 15km from Zawiya. Ayeb added that rebel scouts who had returned from Zawiya claimed that local people there were waiting for the rebels to reach the city's outskirts to join their fight against Gaddafi. "They are waiting for the rebels to come and they will join them," he said.

In other fighting, on two fronts well to the east of Tripoli, at Brega and near Misrata, at least 21 rebels and six soldiers were killed over the past two days, with some 50 rebels wounded. Neither side had claimed major advances in the previous 24 hours.

Libya's state news agency said a Nato air strike killed six men in Brega. Nato said it had targeted two armoured vehicles there. Judging by impact craters, wrecked buildings and burned-out tanks, Nato warplanes have also bombed government military targets on the route of the advance to Zawiya over the past week.

On Libya's most easterly front, at least 21 rebels and government soldiers were killed in fighting for the oil terminal of Brega in the past two days, hospital workers said. A volunteer at the hospital in Ajdabiyah, where fighters wounded in Brega are taken, said 15 rebels had been killed and about 50 wounded. He said the bodies of six government soldiers were brought in on Friday.

The Libyan state news agency Jana reported that six "martyrs" were killed in a Nato raid on Brega.

In fighting on the eastern front in Misrata, much closer to Tripoli, at least six rebels had been killed in the previous 24 hours, rebel sources said.

A rebel spokesman involved in the Brega battle said opposition forces were fighting their way south from the residential town towards the oil terminal, 15km away and had knocked out two government tanks.

Gaddafi's forces still control the port, oil terminal and refinery in Brega, which has changed hands several times over months of fighting. His opponents are intent on seizing the port's oil facilities to begin exporting oil.