MISRATA, Libya (AFP) – Snipers, cluster bombs and intense shelling are spreading panic in Misrata, an AFP reporter said on Monday, as a doctor reported 1,000 people killed in six weeks of fighting in the besieged city.

With fears growing that refugees will attempt a chaotic mass escape by sea from the city of 400,000, UN chief Ban Ki-moon called for a ceasefire and a political solution to the two-month-old conflict in Libya.

The International Organisation for Migration warned that the vast numbers wanting to flee Misrata, about 215 kilometres (130 miles) east of Tripoli, was threatening to overwhelm an international sea rescue operation.

The IOM said nearly 1,000 stranded people had been taken out on Monday, but that thousands more were awaiting rescue in increasingly perilous circumstances.

Hussein al-Fortia, a school headmaster-turned-rebel, said fighting had been "awful" over the past weeks, with forces loyal to Libyan leader Moamer Kadhafi attacking from three sides and firing rockets from kilometres (miles) away.

He said "yesterday and today it is better," with aid having come from outside and rebels pushing forward."

He did not know how many insurgent fighters there are. "Maybe there are 3,000, maybe 5,000 -- no one knows because we are not fighters."

He confirmed that some families, understandably, are eager to leave the city.

"Staying in Misrata is terrible. Everyone in Misrata is on the front line," he said.

The administrator of the main hospital in Misrata, Doctor Khaled Abu Falgha, told reporters 17 people were killed on Sunday.

In all, 1,000 people are estimated to have been killed in the fighting that broke out in Misrata nearly six weeks ago, while another 3,000 people have been wounded, Abu Falgha said.

"Eighty percent of the deaths are civilians," he said.

Human Rights Watch quoted doctors as saying more than 267 bodies had been taken to morgues as of April 15, the majority of them civilians, but that the actual toll was higher because some dead had not been taken in.

Kadhafi's son, Seif al-Islam, denied civilians were being targeted.

"We didn't commit any crime against our people," he said in an interview with The Washington Post published Sunday.

Seif told the Post in an interview in Tripoli that evidence of Libyan forces firing on anti-government demonstrators is false, likening it to eventually unsubstantiated claims of pre-war Iraq hiding weapons of mass destruction.

"It's exactly like the WMD," he said. "WMD, WMD, WMD, go and attack Iraq. Civilians, civilians, civilians, go and attack Libya. It's the same thing.

"I am not going to accept it, that the Libyan army killed civilians. This didn't happen. It will never happen."

NATO is currently enforcing a United Nations-mandated no-fly zone designed to protect civilians, and Western allies have called for the end of Kadhafi's four-decade rule.

Speaking in Budapest, the UN's Ban called for an immediate ceasefire and a political solution to the conflict, saying the United Nations would open a humanitarian mission in Tripoli.

"We have three objectives: first, an immediate, effective ceasefire; second, to extend our humanitarian assistance to the needy; third, we have to continue to have a political dialogue and a political resolution to the issue," Ban said.

"Considering the magnitude of the crisis if the fighting continues, it is absolutely necessary that Libyan authorities stop fighting and killing people," he said.

Hospital administrator Abu Falgha said the last week has seen worsened injuries from cluster bombs, requiring many amputations in Misrata.

Cluster bombs, which spray deadly bomblets indiscriminately over a large area, are banned by most countries.

Snipers too are spreading fear, striking people down randomly in the street.

Among them is 10-year-old Mohammed, who writhes in a hospital bed. His eyes are open, but he is unconscious, and it is unlikely he will ever regain consciousness.

"It was a high-velocity bullet. It went in the left side of his head and out the other side, taking brain matter with it," Doctor Abdul Kather Muqtar explained.

With residents feeling ever more in danger, many want to leave but the only way out is by sea as Kadhafi's forces surround the city.

In Geneva, the IOM said a chartered ferry had evacuated 971 stranded people on Monday, mostly Ghanaians, and was headed for Benghazi, where those deemed physically able would later be taken to the Egyptian border for repatriation.

The arrival of the Greek vessel on Sunday saw hundreds of panicked refugees blocking a key road to the harbour and demanding to be allowed aboard, witnesses said.

Jeremy Haslam, IOM chief in Libya, said the situation was eventually calmed by the rebels manning checkpoints at the port and some of the Libyans being allowed on the ferry.

But he said he was worried the movement could be just the tip of the iceberg of an attempted mass escape by sea by many of Misrata's 400,000 residents.

Such an exodus would overwhelm the evacuation operation mounted by the IOM, the Qatari government and the French group Doctors Without Borders, he warned.

The current plan calls for the IOM and other organisations to take non-Libyan refugees from Misrata -- mostly Egyptians, Chadians, Ghanians and people from Niger -- to a transit camp in the eastern rebel stronghold of Benghazi, where they would be sent to Egypt for repatriation.

The IOM said thousands more are awaiting rescue and that the situation on the ground is getting increasingly difficult for further evacuation missions.

"We have a very, very small window to get everyone out. We do not have the luxury of having days, but hours," said Pasquale Lupoli, IOM?s regional representative for the Middle East.

"Instead of carrying out several further missions that will go into next week, what we now need is to have a ship that can accommodate at least 4,000 people and do one last mission that can take everyone out at the same time immediately," she added.