A coalition of nations including Britain, France and the United States are ready to join military action against Muammar Gaddafi's forces in Libya.
Here are details of their contributions:
FRANCE
A French warplane fired the first shot in the operation on a Libyan military vehicle at 1645 GMT, after talks between world leaders in Paris hosted by President Nicolas Sarkozy. Three more air strikes followed.
He said earlier that French jets were overflying the rebel bastion of Benghazi, preventing Gaddafi's air strikes.
Around 20 French warplanes were involved in operations over Libya, the French defence ministry said.
France has about 100 warplanes, mainly Rafale and Mirage 2000 jets. Air bases at Solenzara in Corsica and in Ndjamena in Chad were also on alert.
The aircraft carrier Charles de Gaulle will be deployed to Libya tomorrow.
BRITAIN
Prime Minister David Cameron said British forces were in action over Libya late today.
Britain has moved Tornado and Typhoon fighter jets to bases near Libya and is also offering air-to-air refuelling and surveillance aircraft.
The country has an airbase in Cyprus, where three of its airborne warning and control system (AWACS) planes were recently stationed.
Two frigates, HMS Cumberland and HMS Westminster, were already in the Mediterranean.
UNITED STATES
Secretary of State Hillary Clinton said the United States would deploy its "unique capabilities" but gave no further details.
US tomahawk cruise missiles hit Libya late today, the Pentagon said.
Washington has F-15 and F-16 fighter jets in Sicily, while the USS Barry and the USS Stout, both destroyers equipped with sea-to-ground Tomahawk missiles, are in the Mediterranean.
The USS Bataan, a helicopter-carrying amphibious assault ship, and two other vessels have also been deployed to relieve the USS Kearsarge and the transport docking ship USS Ponce in the Mediterranean. The Bataan was due to leave the state of Virginia on Wednesday.
The US also has three submarines in the Mediterranean capable of firing Tomahawk missiles.
CANADA
Seven CF-18 jets and a C-17 Globemaster transport plane have headed for the Mediterranean, with another C-17 due to be deployed later.
ARAB NATIONS
Qatar said it will contribute to the no-fly zone but has not given details, while a UN diplomat said the United Arab Emirates will participate.
NATO
The 28-nation alliance was discussing whether to participate, but France has indicated that it would prefer NATO did not.
AWACS planes have been flying 24 hours a day in the region for the past week as part of a NATO anti-terror mission. The alliance also decided last week to deploy three ships to the area.
ITALY
Prime Minister Silvio Berlusconi offered the use of its seven air bases and held out the possibility of using its own air force and navy.
NORWAY
Prime Minister Jens Stoltenberg said six F-16 warplanes would be in place "within a few days".
DENMARK
The defence ministry said four F-16s, two reserve fighter jets and a transport plane had been sent to a military base in Sicily.
BELGIUM
Defence Minister Pieter De Crem said Belgium could deploy four of the six F-16 fighter jets it has committed to NATO, plus an anti-mine ship.
SPAIN
Prime Minister Jose Luis Zapatero said four F-18 fighter planes and an air-to-air refuelling plane would leave today for an Italian base.
NETHERLANDS
A diplomat in Paris said the Netherlands would join military action.
GREECE
Prime Minister George Papandreou volunteered the use of the island of Crete, which lies northeast of Libya, a diplomat in Paris said.