WASHINGTON: US and British forces have fired at least 110 Tomahawk cruise missiles into Libya against Moamer Kadhafi's air defense sites, a top US military officer said Saturday.

A US warship fired Tomahawk cruise missiles into Libya on Saturday, targeting Moamer Kadhafi's air defense sites, a senior US military official said.

The US engaged with “command and control logistics (and) cruise missiles” in its first strikes near Libya's coast, “because that's where the integrated missile defense systems are and of course te other air defense related facilities,” notably around Tripoli and Misrata, the official said.

The US operation -- named “Odyssey Dawn” -- followed initial missions by French warplanes, which carried out four air strikes Saturday, destroying several armoured vehicles of Kadhafi forces.

Two US Navy destroyers and three US submarines were positioned in the Meditteranean near Libya, all of which are equipped with Tomahawk missiles.

No US ground troops will be sent into Libya, US President Barack Obama said Saturday after announcing he authorized the cruise missile strikes launched minutes earlier against strongman Moamer Kadhafi's forces.

“Today, I authorized the armed forces of the United States to begin a limited military action in Libya,” said Obama, who is in Brazil on an official visit.

Western forces bombed fuel tanks feeding the rebel-held city of Misrata, east of Tripoli, on Saturday, a Libyan army spokesman said on state television.

“The 'Crusader enemy' has bombed fuel tanks feeding the city of Misrata and the surrounding regions,” the spokesman said.

The report came as the United States and France announced the launch of air strikes on targets in Libya.

Earlier on Saturday, rebels in Misrata, 210 kilometres (130 miles) from the Libyan capital, said they had beaten back an assault by forces loyal to Libyan strongman Moamer Kadhafi.

Meanwhile the British Prime Minister David Cameron said on Saturday that British forces were in action over Libya as part of a UN-sanctioned intervention to stop Moamer Kadhafi's forces crushing an uprising,.

“Tonight, British forces are in action over Libya. They are part of an international coalition that has come together to enforce the will of the United Nations and to protect the Libyan people,” Cameron said.

“We have all seen the appalling brutality that Colonel Kadhafi has meted out against his own people and far from introducing the ceasefire he spoke about he has actually stepped up the attacks and the brutality.”Speaking after a meeting of the British government's emergency committee, COBRA, in London, he said of the military intervention: “What we are doing is necessary, it is legal and it is right.”The leader did not give any details on what form the British action, codenamed “Operation Ellamy”, was taking but he had announced on Friday that British Tornado and Typhoon fighter jets were being moved to bases near Libya.

Britain has an airbase at Akrotiri in Cyprus which could be used to launch attacks. It also has two frigates, HMS Cumberland and HMS Westminster, already in the Mediterranean.

Cameron's announcement came after a French warplane fired the first shot on a vehicle in Libya at 1645 GMT in an operation to enforce a UN resolution calling for a no-fly zone and protection of Libyans from Kadhafi's forces.

The intervention is backed by Western countries and Arab allies.