Forces loyal to Libya's transitional government have launched a major assault on the city of Sirte, one of the last pro-Gaddafi strongholds.
The BBC reports hundreds of vehicles have advanced on the city from both the east and the west and are close to the centre in what is by the far the biggest assault in recent days.
A reporter on the city's outskirts says Sirte has been targeted by sustained tank and mortar fire and there are huge columns of smoke across the city, with many buildings on fire.
Thousands of civilians have already left Sirte but many more are thought to have remained behind.
The attack came just hours after Colonel Muammar Gaddafi urged Libyans to take to the streets "in their millions" to resist the interim leaders.
The ousted leader's whereabouts remain unknown.