NATO on Sunday pounded Tripoli hours after Britain's top diplomat met rebel chiefs in Libya and Russia voiced concerns the alliance's military operation is sliding towards a land campaign. Warplanes launched intensive air raids on the Libyan capital and its eastern suburbs,where several explosions were heard,as NATO kept up its pressure on strongman Muammar Gaddafi. British Foreign Minister William Hague yesterday met leaders of rebels who have been fighting to oust Gaddafi after NATO deployed attack helicopters for the first time. "We are here today for one principal reason - to show our support for the Libyan people and for the National Transitional Council,the legitimate representative of the Libyan people," Hague said in a statement. Hague,accompanied by international development minister Andrew Mitchell,held talks with the head of the rebel National Transitional Council Mustafa al-Jalil. He also toured Benghazi's landmark seafront as well as a medical centre treating war wounded. "Gaddafi should leave immediately," Hague said. He told reporters Britain would also support demining efforts in Misrata,the main rebel-held city in western Libya,and deliver "more equipment,uniforms,bullet-proof jackets" to rebel fighters. Hours after Hague's trip to the rebel capital,a series of NATO air strikes targeted Tripoli. Four blasts shook Tripoli at around 2:30 am (6000 IST) on Sunday after two powerful but distant explosions were felt in the centre of the capital at around 6:30 pm (1000 IST) on Saturday,followed by several others within a few minutes. Witnesses said the explosions came from Tajura,a suburb that has often been targeted by NATO since an international coalition began military operations against Libya on March 31 to stop strongman Moamer Gaddafi attacking civilians. Britain's defence ministry said today its Apache helicopters returned to the NATO campaign over Libya,destroying a multiple missile launcher operated by Gaddafi forces near the eastern oil hub of Brega. "At sea,HMS Ocean launched her British Army Apaches against a multiple rocket launch system positioned on the Libyan coast near Brega," Major General Nick Pope,spokesman for the Chief of Defence Staff,said in a statement. British Tornado strike planes separately joined other NATO aircraft in a "major strike on a large surface-to-air missile depot" in the Libyan capital Tripoli,Pope added. In its latest operational update issued,NATO said it struck a command and control node,missile storage facility and military installation in Tripoli and rocket launcher,barracks and two checkpoints near Brega. Moscow,which is calling for a negotiated solution to the conflict,expressed alarm as the NATO campaign entered a new phase. "We consider that what is going on is either consciously or unconsciously sliding towards a land operation," Foreign Minister Sergei Lavrov said.