BENGHAZI (AFP) - Libyan regime forces Saturday shelled fuel depots in Misrata and dropped mines into its harbour using helicopters bearing the Red Cross emblem, rebels said as they braced for a ground assault. Fierce clashes near the western Libyan town of Zintan killed at least nine rebel fighters and wounded 50 others on Saturday, an AFP correspondent and medics said. The latest fighting came as Amnesty International lashed out at the government of Libyan leader Moamer Gaddafi, saying its more than two-month "horrifying" siege of Misrata could be a war crime. "There are still attacks by Grad missiles and our fighters are still resisting," said Colonel Ahmed Omar Bani, military spokesman of the rebels' Benghazi-based National Transitional Council. "They tried again to destroy the Misrata port but our fighters didn't allow them to do that," he said, adding Gaddafi loyalists had switched tactics and were now focusing their offensive on fuel depots. The rebels also accused Gaddafi forces of using helicopters disguised as humanitarian aircraft on Thursday and Friday to drop mines into the harbour of Misrata, the major western hold-out of the insurgents. "They had Red Crescent and Red Cross markers so that anyone who sees them thinks it is for humanitarian aid," said Suleiman Fortiya, who represents rebels in Misrata. A NATO official told AFP a ship involved in the the coalitions' operations had observed a number of helicopters over Misrata on Thursday, which came under fire from rebel forces. "We are aware of reports that the helicopters were marked with the Red Cross," said the NATO official, adding no humanitarian flights had been notified for the Misrata area on that day. A spokeswoman at the ICRC's Geneva headquarters said they had received similar reports but could not confirm them, as the organisation currently has no team on the ground. Deputy Foreign Minister Khaled Kaim said Friday there would be no let-up in the government's attempts to block off the maritime lifeline to Misrata, which he said allows "ships to bring arms to the city and then to evacuate some criminals." The rebels said they were bracing for a new ground assault on Misrata. The rebels said on Saturday that Italy has agreed to supply them with weapons "very soon" to fight Gaddafi's forces, although foreign ministry officials in Rome explained it was "self-defence material." The Italian officials said these would not be assault weapons but did not give further details. Representatives of the international community decided Thursday in Rome to provide emergency humanitarian aid of $250 million (175 million euros) to the rebels and said frozen overseas assets of the Gaddafi regime, estimated at $60 billion, would used later for aiding the Libyan opposition. The immediate funds made available are far less than the $3 billion sought by the rebels, but their leader, Mahmud Jibril, described it as "a good start." He said $3 billion represents "a six-month budget." Tribal chiefs called in a meeting Friday for a "general amnesty law which will include all those who were involved in the crisis and took up arms." But doubts were cast on the proposal of National Conference for Libyan Tribes, as its statement referred to rebels as "traitors" and pledged not to "abandon" or "forsake" Gaddafi, whose ouster the insurgents are demanding. A resident in Zintan said a number of Grad rockets had also struck the rebel-held western town and that fighting was going on in Riayna, a few kilometres to the east. The mountainous area around Zintan, southwest of Tripoli, was one of the first to rise up against Gaddafi.