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 April 12.

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.

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.

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.