Smoke and flames pour from the Libyan Navy frigate Al Ghardabia, after it was hit during an airstrike by Tornado bombers of Britain's Royal Force on the port area of Tripoli, in the early hours of Friday May 20 (Photo: AP)
Libyan officials said late on Saturday that the alliance had attacked close to Gaddafi's Bab al-Aziziyah complex, and Reuters Television pictures showed a column of smoke rising over the capital.
However, there was no immediate word on what the target of the attack was, and reporters escorted by Libyan officials were unable to get close to the site.
NATO says its campaign has crippled Tripoli's ability to attack rebels trying to overthrow Gaddafi and effectively forced the Libyan leader into hiding. Overall the conflict is deadlocked as rebel attempts to advance on Tripoli have stalled.
Earlier on Saturday, the Brnieq opposition newspaper reported on its website that shelling of Misrata's eastern and western outskirts damaged houses but no one was hurt. There was no independent confirmation of the attack.
Three months into the uprising against Gaddafi's four-decade rule, rebels control the oil-producing east of the country and pockets in the west including the port city of Misrata, where hundreds have died in a siege and weeks of fierce fighting.
NATO says its bombing campaign against Libyan government forces has helped rebels to consolidate their positions in Misrata, the only western city in rebel hands.
The alliance took command of a U.N.-authorised mission nearly two months ago to stop Gaddafi's forces attacking civilians, and Western governments including the United States, Britain and France are under pressure to show results.
NATO said it conducted 157 air sorties on Friday. Its targets included a command-and-control node and an armoured vehicle storage depot near Tripoli, and three surface-to-air missile launchers around Sirte, Gaddafi's hometown.
Tripoli calls the rebels criminals and al Qaeda militants and says NATO's bombing is armed aggression by Western nations bent on grabbing Libya's oil.
Libyans armed with guns and a knife stormed a bus carrying foreign journalists in Tripoli on Saturday and a soldier fired volleys of gunfire into the air to disperse the crowd, said a Reuters journalist on the bus.
No one was hurt in the attack but it reflected anger in government-controlled territory over severe petrol shortages, NATO air strikes and government and state media reports that foreign journalists misrepresent the news.
In the contested Western Mountains region, Gaddafi forces surrounded the eastern section of Ryna, positioned snipers on roofs, kidnapped young men and looted stores, Jemaa Ibrahim, a rebel in nearby Zintan, told Reuters by telephone on Saturday.
The soldiers, who included African mercenaries, asked residents to leave their homes and many fled under duress, some coming to Zintan, he said. There was no independent confirmation of his report.