Investigators have evidence that Libyan leader Moammar Gadhafi ordered mass rapes and bought containers of sex drugs to encourage troops to attack women, the chief ICC prosecutor said Wednesday.

Luis Moreno-Ocampo said he may ask for a new charge of mass rape to be made against Gadhafi following the new evidence.

Moammar Gadhafi's forces attacked Libya's third-largest city Misrata on Wednesday drawing no response from NATO despite a pledge by the alliance to press its air war, a rebel spokesman said.

Between 2,000 and 3,000 Gadhafi troops attacked the Mediterranean port city from the south, west and east, killing 10 rebel fighters and wounding 26, the spokesman Hassan al-Galai, told Agence France Presse by telephone from the city.

NATO pledged on Wednesday no let-up of its relentless air war in Libya after Moammar Gadhafi vowed he would never surrender, even as bombs rained down on his Tripoli residence.

Spain, meanwhile, joined the growing list of countries which recognize the rebels seeking to topple Gadhafi as the sole representative of Libya's people, leaving the strongman more isolated than ever.

U.S. Secretary of State Hillary Clinton left here Wednesday for Abu Dhabi to consult with countries backing military action in Libya and looking at more ways to help the Libyan opposition.

The talks in the United Arab Emirates (UAE) capital on Thursday come after President Barack Obama said NATO's mission in Libya was forging "inexorable" advances that meant it was only a matter of time before defiant Moammar Gadhafi's departure.

Libyan leader Moammar Gadhafi has vowed to fight to death in a surprise speech during the heaviest day of NATO shelling in the capital Tripoli.

Gadhafi's voice suddenly emerged on Libyan television Tuesday afternoon -- barely an hour after the last some 30 NATO strikes pounded the capital.

Russia is not playing the role of mediator in the Libya conflict, Foreign Minister Segei Lavrov said on Tuesday after a Kremlin envoy was dispatched to the rebels' stronghold in Benghazi.

President Dmitry Medvedev's envoy Mikhail Margelov met Libyan rebel leaders on Tuesday in the first trip by a top Russian official to their stronghold, as NATO warplanes pounded the capital.

Four explosions shook the center of the Libyan capital Tuesday, sending plumes of smoke billowing across an area in which strongman Moammar Gadhafi has his residence, an Agence France Presse correspondent witnessed.

The first blast rocked Tripoli at 10:45 am (0845 GMT) and was followed by three others.

NATO air raids targeted the communications of Moammar Gadhafi's battered regime in Libya on Monday, hitting offices of the state broadcaster and his military intelligence headquarters, officials said.

The air strikes came ahead of a visit to Libya by an envoy from Russia, which has raised concerns about the scope of the military campaign.

NATO pounded Tripoli on Sunday 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.

U.S. Defense Secretary Robert Gates said it was only a matter of time before aides to Libyan leader Moammar Gadhafi abandon him.

British Foreign Secretary William Hague arrived in the Libyan rebel stronghold of Benghazi on Saturday for talks with the opposition's leadership, the Foreign Office said.

Hague, who is accompanied by international development minister Andrew Mitchell, will meet with Mustafa Abdul Jalil, the chief of the rebel National Transitional Council, it said in a statement from London.