Loud explosions rocked Tripoli late Wednesday near the residence of Libyan leader Muammar Gaddafi as global powers gathered for talks on mapping out a democratic future for the North African nation.
The first blast shook central Tripoli around 8pm (GMT), followed 15 minutes later by a stronger explosion near a hotel housing foreign journalists.
Regime spokesman Mussa Ibrahim said NATO pounded the Libyan capital with more than 60 bombs on Wednesday, killing 31 people and causing dozens of injuries.
The explosions came after up to 3,000 Gaddafi troops attacked Libya's third-largest city Misrata in a three-pronged movement from the south, west and east, rebel spokesman Hassan al-Galai told AFP by telephone from the city.
Twelve people were killed and 33 wounded in the fighting in which Gaddafi's forces deployed gunships, tanks and Grad rocket launchers as well as mortars, Galai said.
Misrata is the most significant enclave in western Libya captured by the rebels since the start of the uprising in mid-February.
International powers were gathering for talks in the United Arab Emirates on Thursday to discuss the crisis in Libya, with the nation's veteran leader having vowed never to surrender despite the NATO-led military campaign.
"With each meeting, international pressure is growing and momentum is building for change in Libya," said Victoria Nuland, spokesperson for US Secretary of State Hillary Clinton, as the US delegation arrived in Abu Dhabi for the third International Contact Group talks.
Two dozen countries, including key NATO allies Britain, France and Italy, as well as delegates from the United Nations, the Arab League, and the Organisation of Islamic Conference are due to attend the talks.
As the military, political and economic pressure mounts on Gaddafi to step down, the group will discuss "what a post-Gaddafi Libya ought to look like," a senior US official told reporters on condition of anonymity.
Another US administration official said the Contact Group would discuss the dire need for funding for the rebel National Transitional Council.
The opposition has complained that little has happened since the group last met on 5 May in Rome when Clinton and her partners agreed on a new fund to aid the rebels and promised to tap frozen assets of Gaddafi's regime.
NATO allies pledged on Wednesday to stay in Libya "for as long as necessary" and commit the "necessary means" to the military campaign as they extended the operation for another 90 days until late September.
"All ministers agreed we will keep up the pressure for as long as it takes to bring this to an early conclusion," NATO Secretary General Anders Fogh Rasmussen said after the meeting in Brussels.
But the top US uniformed commander Admiral Michael Mullen conceded the Libya campaign was making "very slow progress," while French Defence Minister Gerard Longuet played down expectations of a quick end to the war.
With only eight out of 28 NATO members carrying out air strikes, NATO Secretary General Anders Fogh Rasmussen as well as US and British defence chiefs prodded allies to help ease the burden on air crews showing signs of fatigue.
US Defence Secretary Robert Gates named three countries that should mull taking part in air strikes -- Spain, Turkey and the Netherlands -- and urged Germany and Poland, which are not participating at all, to consider joining the campaign, said officials familiar with the discussions.
Meanwhile, in a new twist the International Criminal Court's chief prosecutor, Luis Moreno-Ocampo, said investigators had evidence Gaddafi ordered mass rapes and bought containers of sex drugs for troops to attack women.
"Now we are getting some information that Gaddafi himself decided to rape and this is new," Moreno-Ocampo said at the United Nations.
China said it would welcome a visit "in the near future" by the Libyan rebels, as Beijing stepped up contacts with both sides in the conflict.
Chinese diplomats have so far held two confirmed meetings with the rebel National Transitional Council in Benghazi.
"We are ready to receive a visit from NTC representatives in the near future," the official Xinhua news agency quoted foreign ministry official Chen Xiaodong as saying.
"We believe the current situation is untenable and it's time to come up with a solution."
A flurry of diplomatic activity seemed to indicate that China -- which has significant economic interests in Libya -- was stepping up its involvement in efforts to defuse the crisis.
On Wednesday, Chinese Foreign Minister Yang Jiechi told his visiting Libyan counterpart Abdelati al-Obeidi that securing a ceasefire should be the "top priority" of both sides in the months-long conflict.