BENGHAZI: Libyan rebels begged for more Nato air strikes on Thursday, saying they faced a massacre from government artillery barrages on the besieged city of Misrata, but Western allies squabbled over how to respond.

Rebels said a hail of Grad rockets fired by besieging forces into a residential district of Misrata, Libya's third largest city, had killed 23 civilians, mostly women and children.

Aid organisations warn of a humanitarian disaster in Misrata, the lone rebel bastion in western Libya, where hundreds of civilians are said to have died in a six-week siege.

Nato warplanes later launched strikes on the Libyan capital Tripoli. State television said there were civilian casualties.

Reuters correspondents heard four blasts and anti-aircraft fire, and saw plumes of smoke to the southeast.

US Secretary of State Hillary Clinton expressed concern at a Nato meeting in Berlin over “atrocities” in Misrata but gave no hint Washington was prepared to re-engage in air strikes.

Reflecting concern at strains in the alliance over the bombing campaign, Clinton called for Nato to maintain “resolve and unity” against Muammar Gaddafi, saying he was trying to test Western determination.

Papering over differences, Nato foreign ministers pledged in a joint declaration to provide “all necessary resources and maximum operational flexibility” for the air campaign to maintain a “high operational tempo against legitimate targets”.

But several allies rebuffed calls from France and Britain to contribute more to the air attacks, conducted under a United Nations mandate to protect civilians and US officials said allied commanders had not requested greater resources.

“A massacre...will take place here if Nato does not intervene strongly,” a rebel spokesman in Misrata told Reuters by phone. Reports of casualties are hard to verify independently because journalists cannot reach the area.

Al Jazeera television showed hundreds of Misrata residents demonstrating after the dawn attack. “The blood of martyrs will not be in vain,” they chanted, waving the rebel flag.