Media playback is unsupported on your device Media caption Alain Juppe: 'Nato must play its role fully'

Nato must do more to destroy heavy weaponry used by Muammar Gaddafi's forces in Libya, the French and British foreign ministers have said.

Libyan civilians remain at risk, France's Alain Juppe said, despite the ongoing Nato-led bombing campaign.

The UK's William Hague urged Nato allies to intensify military operations, but a Nato general said the alliance was "doing a great job".

Libyan rebels opposing Col Gaddafi have been pushed back despite the air raids.

Pro-Gaddafi forces launched fresh artillery attacks on the rebel-held city of Misrata on Tuesday.

The last rebel-held area in the west, Misrata has been under siege for more than six weeks, with rights groups warning of a shortage of food and medical supplies.

'Intensify efforts'

Commenting on the military campaign, French Foreign Minister Alain Juppe said efforts in Libya were so far "not enough".

Analysis What Mr Juppe's comments represent is an increasing sense of frustration at the way the military operation is going. For several weeks there have been interventions by both Nato and other aircraft over Libya and yet Col Gaddafi's forces are still able to use heavy weapons against civilians in Misrata. There is a fear that we could be heading towards some sort of stalemate - something that for the French and others would be unacceptable. Make no mistake, there is an implied criticism of Nato. The frustration creeping in here also exists in London. The French find it embarrassing that several weeks after this operation started the civilians in Misrata are still being hit with heavy weapons.

"Nato must play its role fully. It wanted to take the lead in operations," Mr Juppe said.

Mr Hague later echoed Mr Juppe's comments: "We must maintain and intensify our efforts in Nato.

"That is why the United Kingdom has in the last weeks supplied additional aircraft capable of striking ground targets threatening the civilian population.

"Of course it would be welcome if other countries also did the same," he said on arrival at a meeting of EU foreign ministers in Luxembourg.

In France's National Assembly, Defence Minister Gerard Longuet said there was a limit to Nato's current capability.

"Today we have no support in the ground attack role, without which there's no chance of breaking the siege of towns like Misrata or Zenten," he said.

That sentiment was echoed by a senior Libyan rebel, Mustafa Abdel Jalil. He said Nato could not relieve besieged cities and appealed for arms and supplies.

Media playback is unsupported on your device Media caption Dutch Brig Gen Mark Van Uhm said he felt Nato was doing well "with the assets we have"

However, Dutch Brig Gen Mark Van Uhm, head of Nato operations in Libya, said he felt Nato was doing well "with the assets we have".

The alliance had been successful in establishing a no-fly zone, protecting civilians and enforcing an arms embargo, he said, speaking at Nato HQ in Brussels.

Meanwhile in the UK, the Foreign Office confirmed that the most high-profile minister to flee Libya, Moussa Koussa, had left the UK for Qatar, to meet the emirate's government and Libyan representatives.

A spokesman from the UK government said that Mr Koussa was "a free individual, who can travel to and from the UK as he wishes".

Ceasefire rejection

Media playback is unsupported on your device Media caption Moussa Koussa - a former head of Libyan intelligence - said he could not continue in Libya's government

Nato also denied a report made by Libyan state television that a strike by international forces killed civilians in the town of Kikla, south-west of Tripoli, on Monday.

"We can confirm there was an air strike in that region. However, it was 21 km (13 miles) southwest of the town that was mentioned on Libyan TV, Kikla. And the target was two tanks," Gen Van Uhm said.

On Monday, the rebels rejected a ceasefire proposal by the African Union (AU) which the organisation said had been accepted by Col Gaddafi.

The rebels' Transitional National Council (TNC) said it was unfeasible as it did not include a provision for the Libyan leader to step down, but the AU have urged them to reconsider.

The plan included a call for an immediate end to hostilities, unhindered humanitarian aid, protection of foreign nationals, dialogue between opposing sides and an end to Nato air strikes.