Libya's NTC troops renew assault on pro-Gaddafi Sirte

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Media captionAlastair Leithead says anti-Gaddafi fighters have made a "major breakthrough"

Libya's interim government forces are renewing their attack on Sirte, one of the last pro-Gaddafi strongholds.

National Transitional Council (NTC) fighters have surrounded the city and Nato warplanes are reported to be blasting targets inside.

It comes a day after NTC troops launched a surprise assault on the birthplace of the ousted Libyan leader, taking them close to the city centre.

Meanwhile in Tripoli, Libyan officials say they have found a mass grave.

The site is believed to contain the remains 1,270 people killed by Col Gaddafi's security forces in a massacre at Abu Salim prison in 1996.

And in the southern town of Ghadames, on the border with Algeria, NTC soldiers repelled an attack by around 100 pro-Gaddafi forces and Algerian and tribal "mercenaries", officials said.

At least eight NTC soldiers were reportedly killed in the attack. Military spokesman Ahmed Bani told a news conference they had information the attackers were related to Col Gaddafi's son Khamis.

'Cautious advance'

Troops were reported to be setting up new roadblocks and checkpoint, posting snipers at various key points and cleaning their guns in preparation for a final assault on Sirte.

Nato planes could be heard buzzing overhead. The alliance confirmed it carried out several sorties on Saturday around Sirte and said it had hit several military targets.

Fighter Ahmed Mohammed Tajuri in the west of the city told AFP they had been ordered to leave downtown Sirte on Saturday evening "because Nato has a mission to do there", without giving more details.

One fighter on the east of the city told the AFP news agency that they had been told by their commanders to keep their guns ready.

"We expect fierce urban battle once we fully enter Sirte," Maatiz Saad said.

The BBC's Alastair Leithead, with the anti-Gaddafi forces in the east of Sirte, said the troops are advancing steadily and cautiously towards Sirte.

They appear to be intent on taking and holding the farms and dusty villages on either side of the main coastal road - making sure there are no pro-Gaddafi forces remaining to call in rockets or slow the main advance further, he says.

Our correspondent has seen a number of civilians fleeing from Sirte who are clearly shaken and nervous, not knowing if the NTC troops have come to liberate or persecute them. Some appear to be unaware that Tripoli fell more than a month ago.

NTC fighters tried to push into Sirte last weekend but were driven back by pro-Gaddafi forces entrenched in the city.