Western warplanes bombed civilian targets in Libya's capital today, causing casualties, state media said, after the launch of a multinational air campaign against Libyan leader Muammar Gaddafi.

"Civilian targets are being bombed by the 'Crusader' enemy fighter planes in Tripoli," state television said.

A Libyan army spokesman told the television that western forces had also bombed fuel tanks feeding the rebel-held city of Misrata, east of Tripoli.

Earlier witnesses told AFP that several loud blasts were heard east of Tripoli and that "balls of fire" could be seen on the horizon. "We don't know where the explosions occurred," a resident of Tripli's eastern suburb said.

Another witness said the blasts target an army battalion stationed about 20 kilometres east of Tripoli.

France and the United States said today they had launched strikes on Libya as part of a UN Security Council resolution authorising the use of force to impose a no-fly zone on Gaddafi's regime.

A US warship fired Tomahawk cruise missiles, targeting Gaddafi's air defence sites, a senior US military official said, while the French military said its warplanes carried out four air strikes.

The operations were to continue through the night, the military said.