Anti-government protesters in the Libyan capital Tripoli have come under heavy gunfire, reports say, as state TV showed pictures of embattled leader Muammar Gaddafi addressing supporters.

There are reports of deaths and injuries in several locations, but no reliable information about casualties.

Meanwhile, the head of the UN has warned of a growing crisis of refugees and food shortages.

Ban Ki-moon said more than 1,000 people had died in the unrest so far.

Protests in Tripoli resumed on Friday as those seeking the overthrow of Colonel Gaddafi emerged from mosques following Friday prayers.

A group of protesters in the Suq al-Jumaa area was confronted by a force of troops and militiamen who opened fire on them as they headed towards Green Square, witnesses said. Snipers on rooftops are also reported to have fired on the marchers.

A witness in Suq al-Jumaa told the BBC that he and other protesters had walked into a military trap, and that the crowd had dispersed in the hail of fire. He said he did not know how many people were killed.

Reports of anti-government protesters being fired on have also come from other areas of the capital including Fashloom, Janzour and Zawlyat al-Dahmani.

"Many people are being killed right now in Tripoli, I just got a few phone calls from friends who witnessed people going out of mosques being shot at," one Tripoli resident told the BBC.

"I am very scared to leave the house. I was planning to visit my parents, but they called me and told me not to go out because there's heavy security on the main roads, stopping cars for checks.

"We haven't left the house for six days, apart from going out to buy bread. The city is completely closed."

Outside Tripoli, reports say attempts by pro-Gaddafi forces to take back territory in the cities of Zawiya and Misrata have been repulsed. An elite brigade commanded by Col Gaddafi's son Khamis is believed to be dug in around the capital.

Libyan state TV showed Colonel Gaddaffi speaking from the Tripoli's Green Square old city ramparts, urging the crowd to arm themselves and defend the nation and its oil against anti-government protesters who have taken control of large parts of the country.

"This is the people that brought Italy to its knees," he said, referring to the overthrow of Libya's colonial rulers. "I am amid the masses, and we shall fight, and we shall defeat them.

"We shall destroy any aggression with popular will. With the armed people, when necessary we will open the weapons depots. So that all the Libyan people, all the Libyan tribes can be armed. Libya will become a red flame, a burning coal."

As his supporters waved green flags, the symbol of Col Gaddafi's rule, he said: "Life without dignity has no value, life without green flags has no value. Sing, dance and prepare yourselves."

Later, at a hastily organised news conference at the United Nations in New York, Libyan deputy ambassador Ibrahim Dabbashi described Col Gaddafi, who has been in power for 42 years, as a "madman" and warned that thousands would die in Tripoli because the Libyan leader would never flee and would fight to the end.

He urged all Libyan diplomats across the world to renounce the regime and make it clear that they represented the people, not Col Gaddafi, and called on African states not to send soldiers or aid to his government.

Speaking at a meeting of the UN Security Council in New York, the global body's secretary general urged the council to take "decisive action" on the Libya crisis, saying that "clear and egregious" violations of human rights had occurred.

Mr Ban said 22,000 people had fled Libya via Tunisia, and a further 15,000 via Egypt.

"Much larger numbers are trapped and unable to leave," he added. "There are widespread reports of refugees being harassed and threatened with guns and knives."

He said it was important for neighbouring countries, including those Europe, to keep their borders open to those fleeing the violence.

Mr Ban also said that there was a food crisis inside Libya that the UN World Food Programme expected to worsen. The WFP says Libya's food supply chain is at risk of collapse because imports have not been getting into the country and food distribution is hampered by violence.

Diplomats at the UN Security Council say Britain and France have drawn up a draft resolution with a package of measures aimed at isolating Libya's political and military leaders. Elements could include targeted sanctions, an arms embargo, and a proposed referral of the situation in Libya to the International Criminal Court.

Earlier, an emergency session of the UN Human Rights Council recommended suspending Libya from the body, and authorised an international investigation into the violence in the country with a view to prosecuting those responsible.

White House spokesman Jay Carney said the Obama administration was acting "to put pressure on the regime" to cease the violence.

"Colonel Gaddafi has lost the confidence of his people," he added.

Evacuations of foreign nationals from Libya by sea continued on Friday, although rough weather hampered the operations.

A US-chartered ferry carrying Americans evacuated from Libya arrived in Malta on Friday evening.

Britain has sent a second ship, the destroyer HMS York, to deploy to the sea area near Libya. The frigate HMS Cumberland has picked up more than 200 people and is taking them to Malta.

India is sending warships to the region to evacuate its nationals.

Hundreds of sub-Saharan Africans are said to be fleeing southern Libya into Niger. Many more are stranded in Libya, where they say they are being attacked by people accusing them of being mercenaries fighting for Col Gaddafi.

Nato ambassadors are currently holding emergency talks in Brussels on the situation in Libya, but Secretary General Anders Fogh Rasmussen says the Western military alliance has no intention of intervening.

British Prime Minister David Cameron described the violence in Libya as "appalling and unacceptable", adding: "People working for this regime... should remember that international justice has a long reach and a long memory."