Alliance attempts to silence Gaddafi's 'incitement to violence' against opponents as rebel unity is tested by Younis killing

Nato warplanes have bombed Libyan state TV satellite transmitters in Tripoli in an attempt to stem the incitement of violence against those not loyal to Muammar Gaddafi, the military alliance has said.

A series of loud explosions echoed across the capital before dawn. There was no immediate comment from Libyan officials on what had been hit but state TV was still on the air in Tripoli on Saturday morning.

Nato said the airstrikes aimed to degrade Libyan ruler Gaddafi's "use of satellite television as a means to intimidate the Libyan people and incite acts of violence against them".

"Striking specifically these critical satellite dishes will reduce the regime's ability to oppress civilians while [preserving] television broadcast infrastructure that will be needed after the conflict," said a Nato statement.

The attempt to silence the government's TV broadcasts comes at a sensitive time for the rebels, who appear to be in disarray after the mysterious death of their military chief. Abdel Fatah Younis's body was found on Thursday dumped outside the rebels' de facto capital of Benghazi, along with the bodies of two colonels who were his top aides. They had been shot and their bodies burned.

Nato too has been increasingly embarrassed by the failure of its bombing campaign, now in its fifth month, to dislodge Gaddafi's regime. With the fasting month of Ramadan due to start in August there is growing realisation that the costly campaign will drag on into the autumn and possibly longer.

Nato had originally hoped that a series of quick, sharp strikes would force Gaddafi out.

Eight Nato members have been participating in air campaign in Libya: the US, Britain, France, Belgium, Canada, Norway, Denmark and Italy. They have carried out more than 6,500 strikes.

But the coalition has been gradually fraying amid growing public opposition in Europe to the costs of the campaign – estimated at more than €1bn – at a time of budget cuts and other austerity measures.

The US has been the first to limit its participation, deciding to only provide support to the European allies. Then Italy withdrew its only aircraft carrier and part of its air force contingent. Norway has announced it will pull out all of its F-16 warplanes by Monday.