Heavy fighting in Libyan towns of Zawiya and Ras Lanuf

Forces loyal to Colonel Gaddafi have been engaged in heavy fighting with rebels in key cities.

Reports say tanks and aircraft are being used to attack anti-Government fighters.

The heaviest onslaught is in the town of Zawiya, 45 km (30 miles) west of the capital Tripoli.

There has also been further fighting to the east in Ras Lanuf. From there, the BBC's World Affairs Editor John Simpson reports.