TRIPOLI (AFP) – NATO's chief will hold talks on Libya with British leaders on Wednesday after the alliance battered Moamer Kadhafi's forces even as its top brass raised concerns about the 11-week aerial war.

NATO Secretary General Anders Fogh Rasmussen will meet in London with British Prime Minister David Cameron and Foreign Secretary William Hague for discussions on the military operation.

The talks come as rebels fighting to end Kadhafi's four decades of autocratic rule won more diplomatic recognition and seized Al-Rayayna village, east of the heavily fought-over hilltown of Zintan southwest of Tripoli.

"The fighting here has become even fiercer because the rebels have become stronger but things move slowly," a witness in Zintan told AFP.

"The clashes are unnaturally violent," he added.

And following a three-day pause in NATO strikes on Tripoli, powerful explosions rocked the Libyan capital late Tuesday, with black smoke rising from a site close to downtown.

Senior military officials from Britain and France, key players in the NATO campaign, had earlier expressed concerns about how to maintain the NATO operation just extended for three months from June 27.

"How long can we go on as we are in Libya?" Britain's First Sea Lord, Admiral Mark Stanhope, asked.

"Certainly in terms of NATO's current time limit that has been extended to 90 days, we are comfortable with that. Beyond that, we might have to request the government to make some challenging decisions about priorities."

French General Stephane Abrial, the Supreme Allied Commander of Transformations, warned the issue of resources "will become critical" if the conflict drags on.

"If the operation was to last longer, of course the resource issue will become critical," Abrial said.

NATO said later it "has the resources" to conduct its campaign despite a warning from Washington that reliance on US military could jeopardise the mission.

"We continue to maintain a high tempo of operation," said NATO spokeswoman Oana Lungescu. "It is clear that NATO has the resources to keep up the pressure on the (Moamer) Kadhafi regime. We know it takes time."

In Al-Rayayna, home to some 10,000 residents, Kadhafi forces responded to the rebel advance by firing Grad rockets at the village, which is on a strategic route connecting Zintan and Yefren, two towns rebels hope to seize.

In Tripoli, blasts were heard around 11:30 pm (2130 GMT) on Tuesday, with state news agency Jana saying NATO targeted civilian sites and that the attacks set homes on fire.

Several people had been injured, it added, without elaborating.

Tripoli and its suburbs have been the target of almost daily NATO air raids since it started its military operation on March 31, a month after Kadhafi's forces began a bloody crackdown on pro-reform protests.

In its latest operational update, NATO said Wednesday it struck an air defence support facility in Tripoli and two surface-to-air missile launchers in the vicinity of the city.

NATO also said it hit a truck-mounted gun near Yefren, two armoured fighting vehicles near Brega and three armoured fighting vehicles and a truck-mounted gun in Misrata.

In Washington, politicians grew impatient with the pace of operations.

Republican House Speaker John Boehner gave President Barack Obama until Friday to ask Congress to authorise military action "or withdraws all US troops and resources from the mission."

The White House vowed later to answer critics of the conflict.

"We are in the final stages of preparing extensive information for the House and Senate that will address a whole host of issues about our ongoing efforts in Libya," national security spokesman Tommy Vietor said in a statement.

Polls show the conflict is overwhelmingly unpopular with the US public.

The rebels gained diplomatically when Canada and Panama recognised them as the legitimate representative of Libya's people, while Tunisia declared itself ready to follow suit.

Liberia broke diplomatic ties with Libya one day after US Secretary of State Hillary Clinton pressed African states to demand Kadhafi step down and take tougher action against his regime.

Libya's foreign ministry meanwhile said a visit this week by German Foreign Minister Guido Westerwelle to Benghazi, the rebels' de facto capital, was a "flagrant violation" of Tripoli's sovereignty.

South African President Jacob Zuma said NATO's air campaign abused a UN resolution to protect Libyan civilians for regime change and "political assassinations".

"We strongly believe that the resolution is being abused for regime change, political assassinations and foreign military occupation," Zuma said in a speech to parliament.

He added NATO's actions undermined African Union efforts to find a solution.