The United States?launches a Tomahawk missile in support of Operation Odyssey Dawn in the Mediterranean Seain this handout photo March 19, 2011.

Top leaders from the United States, Europe and the Arab world on Saturday announced the start of military action against Libyan government forces.

The United States Saturday launched the first Tomahawk missile attacks against the Libyan air defense from warships deployed in the Mediterranean.

Speaking on condition of anonymity, a senior U.S. military official said the strikes targeted air defense sites along the Libyan coast. The sites were around Libyan capital Tripoli and western region of Misrata. The official said the strikes were the first stage of the assault that would involve U.S. Navy ships and planes.

France had already taken military action.

French President Nicolas Sarkozy said "our determination is total."

Earlier, several French reconnaissance planes were flying over Libya, a French military source said.

Libyan state TV said a French plane had been shot down near Tripoli. However, French military officials said all their planes had returned safely.

The U.N. Security Council Thursday adopted a resolution to impose a no-fly zone over Libya and authorize "all necessary measures," excluding ground troops, to protect civilians in the embattled country.

A fighter plane was reportedly shot down in the rebel-controlled Libyan city of Benghazi Saturday morning, but the report was later denied by a Libyan spokesman.

Libyan leader Moammar Gadhafi vowed to fight back against "naked aggression" as the missile strikes launched at Saturday night proved grounds for a "crusade war."

He sent letters to western leaders and the U.N. secretary-general, complaining about "interference" in Libyan issues.

In his letter to Obama, Gaddafi said, "If you had found them taking over American cities with armed force, tell me what you would do."

"I have all the Libyan people supporting me and they are prepared to die for me," he said, "I am facing al-Qaeda here."