BENGHAZI, Libya—Col. Moammar Gadhafi's forces Saturday penetrated deep into Benghazi and heavily shelled the rebel capital's residential neighborhoods, threatening to snuff out the month-old Libyan revolution.

The speedy advance of government troops and the deadly barrages of Grad rockets, tank and artillery fire contradicted the Libyan regime's claims of a ceasefire, and defied Thursday's United Nations Security resolution urging Col. Gadhafi to stop killing his own people.

French, U.S. and U.K. forces, meanwhile, launched an attack to destroy Libya's air defenses, joining an international air campaign against the Gadhafi regime.

Col. Gadhafi's forces, deployed some 100 miles south of Benghazi on Friday afternoon, launched a rapid two-pronged armor assault from the south and the west overnight, outflanking rebel defenses. By Saturday morning, regime tanks, some of which witnesses said were later disabled or captured by the rebels, reached a key bridge less than two miles from the rebel headquarters in a courthouse on Benghazi's Mediterranean corniche.

The shelling, which began before dawn, hit neighborhoods across Benghazi, flattening homes and particularly devastating the Bin Najila area in the west of the city. One shell landed in the parking lot of the Ouzo hotel, where many international news organizations still present in Benghazi are based, showering vehicles with shrapnel.