UPDATE 4-Rockets bombard Misrata, rebels say eight killed
* NATO leaders say Gaddafi trying to strangle Misrata
* Rights group says government forces use cluster munitions
* Aid ships evacuate migrants, wounded
(Adds report on cluster munitions, number of dead, quotes)
By Fredrik Dahl and Joseph Nasr
TUNIS/BERLIN, April 15 (Reuters) - Muammar Gaddafi's forces fired salvos of rockets on Friday in a second day of intense bombardment of Libyan insurgents' besieged western stronghold of Misrata, and rebels said fighting had reached the city centre.
A rebel spokesman said eight people were killed and nine wounded in the bombardment. A U.S.-based human rights group accused government forces of using cluster munitions in Misrata.
The rebel spokesman, Abdelsalam, said pro-Gaddafi forces shelled both the centre and a road leading to the port, a lifeline for Misrata's trapped civilians and the main entry point for international aid agencies.
"Today was very tough ... Gaddafi's forces entered Tripoli Street and Nakl al Theqeel road," he said by phone, referring to a main Misrata thoroughfare, the scene of heavy clashes in recent weeks, and the road to the port.
"Witnesses said they saw pro-Gaddafi soldiers on foot in the city centre today. Except for snipers, they usually stay in their tanks and armoured vehicles," the spokesman added.
A government reconnaissance helicopter had flown over the city, he said, despite a no-fly zone mandated by the U.N. Security Council and enforced by NATO warplanes.
The United States, Britain and France accused Gaddafi of trying to strangle Misrata's population into submission in a "medieval" siege. In addition, thousands of migrants are trapped near the port area, trying to get out.
U.S.-based Human Rights Watch said forces loyal to Gaddafi had used cluster munitions in Misrata, endangering civilians, and published photographs of what it said were remnants of them. A Libyan government spokesman denied it.
"It's appalling that Libya is using this weapon," Steve Goose, Human Rights Watch arms division director, said.
"They pose a huge risk to civilians, both during attacks because of their indiscriminate nature and afterward because of the still-dangerous unexploded duds scattered about."
Government forces have laid siege to Misrata for more than six weeks. Hundreds of civilians are believed to have been killed, and the rebels have warned of an impending massacre unless NATO intensifies its air strikes.
Abdelsalam, the rebel spokesman, provided a list which he said was given to him by a doctor in Misrata with the names of 291 people -- including 36 rebels -- killed between Feb 19 and April 15. Many more were wounded.
Libyan officials say they are fighting armed militia with ties to al Qaeda bent on destroying the North African country.
"The Libyan army is not conducting military operations in the city, we are simply fighting back at the attacks by the rebels," government spokesman Mussa Ibrahim said.
"The reports that we are shelling the city, that we are using bombs, are absolutely false," he said in Tripoli.
One defence analyst noted that in urban fighting the defenders usually held the upper hand but he said that if the Gaddafi loyalists took over the port, or cut off it off from the city centre, it would "handicap (the rebels) tremendously."
"If I was the government commander I would be be aiming to do that. The port is key ... as is the communication to and from it," said London-based Paul Beaver.
Television footage showed buildings ripped apart by artillery fire, burnt-out vehicles in rubble-strewn streets, and doctors treating wounded civilians with inadequate resources.
A ship with nearly 1,200 Asian and African migrants, many needing medical attention after weeks with little food or water, left Misrata on Friday for rebel-held Benghazi, an international aid agency said.
Another ship, operated by Medecins Sans Frontieres, departed for Tunisia with 99 people on board, including 65 with wounds, some in critical condition. An MSF spokeswoman described "deplorable conditions" at migrant camps in the city.
(Additional reporting by Mussab Al-Khairalla in Tripoli; Mariam Karouny in Beirut; Stephanie Nebehay in Geneva; Marie-Louis Gumuchian in Tunis; writing by Richard Lough and Fredrik Dahl; editing by Michael Roddy)