BBC News with Fiona MacDonald

An international military operation is

underway

in Libya to

enforce

a United Nations resolution to prevent Colonel Gaddafi's forces attacking civilians. The United States said American and British naval forces have fired more than 100 cruise missiles at around 20 military targets in Libya. Paul Adams reports from Washington.

Within the last few minutes, the director of the US military's Joint Staff, Vice Admiral William Gortney, has given more details about what he described as the first phase of a multi-phased operation. He said 110 cruise missiles had been fired against Libya's air defence and missile systems. This phase he said was all about creating conditions for coalition partners to patrol the no-fly zone established by UN Security Council Resolution 1973.

State TV in Libya said civilian targets had been hit. Earlier, French warplanes destroyed a number of pro-Gaddafi tanks and armoured vehicles near the rebel-held city of Benghazi.President Obama says the United States is part of a broad coalition to answer the calls of a threatened people in Libya, but he

reiterate

d that the US would not deploy troops on the ground.

"I want the American people to know that the use of force is not our first choice, and it's not a choice that I make

lightly

. But we cannot

stand idly

by when a tyrant tells his people that there will be no mercy, and his forces