MISRATA, Libya (AFP) - Libya categorically denied claims on Saturday by a rights watchdog that Moamer Gaddafi's forces were using illegal cluster bombs against rebel fighters in Misrata, as the long-besieged rebel-held town came under heavy fire once again. French Foreign Minister Alain Juppe said a new United Nations resolution to push Libyan leader Moamer Gaddafi into quitting was unnecessary, and German Economy Minister Rainer Bruederle suggested frozen Libyan funds be diverted to the UN to pay for aid to victims of the conflict. US-based Human Rights Watch (HRW) said its researchers reported the use of internationally banned cluster munitions against Misrata, the rebels' last major bastion in western Libya . But a spokesman for the Libyan regime denied the accusations. "Absolutely no. We can't do this. Morally, legally we can't do this," Mussa Ibrahim told journalists. "We never do it. We challenge them to prove it." Insurgents said Gaddafi loyalists were using cluster bombs, which explode in the air and scatter deadly, armour-piercing submunitions over a wide area. "Last night it was like rain," said Hazam Abu Zaid, a local resident who has taken up arms to defend his neighbourhood, describing the cluster bombings. The use of the munitions was first reported by The New York Times. A reporting team for the daily photographed MAT-120 mortar rounds which it said were produced in Spain. "It's appalling that Libya is using this weapon, especially in a residential area," said Steve Goose, HRW's arms division director. "They pose a huge risk to civilians, both during attacks because of their indiscriminate nature and afterwards because of the still-dangerous unexploded duds scattered about," he said. Loud explosions rocked the western city of Misrata and, in the east, heavy fighting was reported as rebel fighters, bolstered by NATO air strikes, pushed on from the crossroads town of Ajdabiya towards the strategic oil town of Brega. Six people were killed and 20 wounded in rocket fire from Gaddafi forces, medics reported. And even further west, NATO air strikes targeted Gaddafi's hometown of Sirte, state news agency JANA reported, without giving details. NATO warplanes had already struck Sirte on Friday, JANA reported, and at the time. Later in the day, the agency reported further air strikes on the region of Al-Hira, 50 kilometres (30 miles) south-west of Tripoli. The blasts in Misrata were accompanied by bursts of gunfire heard coming from the city centre, after NATO flyovers and possible air raids were followed by a lull in shelling and shooting, an AFP correspondent said. Officials at Misrata's main Hikma hospital said overnight it had received five dead bodies and 31 wounded. In Paris, aid organisation Doctors Without Borders (MSF) said it had evacuated 99 people, including 64 war-wounded, by boat from Misrata on Friday to Tunisia. Speaking of the dire conditions in the city, under siege for weeks, MSF Doctor Morten Rostrup said in a statement that "health structures have been struggling to cope with the influx of patients". "With the latest heavy bombardments in Misrata, the situation is worsening, as hospitals have to discharge patients before their treatment is completed in order to treat the new wounded from fighting. Many injured cannot even access medical facilities without further risking their life." Rostrup also said an MSF visiting a nearby migrant camp found that "these people live in extremely difficult conditions, lacking proper shelter and food. They are desperate to go back to their home countries." Tens of thousands of migrants have already fled Libya since the rebellion broke out in mid-February. French Foreign Minister Alain Juppe said a new UN resolution to push Gaddafi into quitting was unnecessary. "We think that given his behaviour, his savage repression of the population, Gaddafi has lost all legitimacy to stay in power," Juppe said in Paris. "That is the view of the United States, of Great Britain, of the 27 member states of the European Union, of the Arab League, and there is no need for a new Security Council resolution to enact this principle." The current resolution "fixes the boundaries of the current intervention in Libya and we are applying it strictly," Juppe said, speaking on the sidelines of a conference on the Arab uprisings staged by his ministry. German Economy Minister Rainer Bruederle has suggested frozen Libyan funds should be diverted to the United Nations to pay for aid to victims of the conflict. The weekly Der Spiegel quoted an internal note from Bruederle's ministry saying Germany had frozen $6 billion (4.1 billion euros) of assets belonging to Gaddafi or the Libyan state in line with UN sanctions. These assets, as well as those seized by other European countries, could be paid into a special UN account "in order to pay for humanitarian aid to ease the distress of the inhabitants of the whole of Libya ", the note was quoted as saying. In Berlin, Russian Foreign Minister Sergei Lavrov called for an immediate ceasefire and for the warring parties to be brought to the negotiating table. UN Security Council Resolution 1973 calls for a ceasefire, but Gaddafi has relentlessly pursued his campaign to retake territory lost to the rebels. NATO Secretary General Anders Fogh Rasmussen denied the air strikes were beyond the scope of the UN resolution. "I have to stress that in the conduct of that operation, we do not go beyond the text or the spirit" of the resolution, he said. Meanwhile, the European Union and NATO deepened their coordination for a potential EU military mission to deliver urgent humanitarian aid to Misrata, diplomats said. The International Organisation for Migration said about 1,200 migrants have been evacuated from Misrata to the eastern rebel stronghold of Benghazi. Most were Bangladeshis and Egyptians. Any EU mission would have to be coordinated with NATO because the 27-nation alliance has several warships and units of warplanes in the Mediterranean.