TRIPOLI, Libya - Libyan government forces pounded the outskirts of the rebel-held city of Misrata on Friday, killing at least 22 people, a hospital physician said.

The doctor at Hikma Hospital, who would only give his first name, Ayman, said Moammar Gadhafi's forces used tanks, artillery and incendiary rockets in the bombardment of Dafniya, about 30 kilometres west of Misrata. He said at least 61 people were wounded in the attacks which began about 10 a.m. local time.

Gadhafi forces had renewed their shelling near Misrata on Wednesday. The city is one of the few footholds rebels have in western Libya and controls the country's largest port.

The doctor said residents had reported no sign of NATO aircraft in the Misrata region. There also were no reports NATO strikes in Tripoli, the capital. NATO had been pounding Tripoli and environs in recent days, stepping up backing for the four-month-old rebel uprising that seeks to oust Gadhafi from power after four decades.

Rebels have taken control of swaths of eastern Libya, although fighting has since come to a stalemate even with NATO support. Misrata remained one of the most important rebel footholds in the Gadhafi controlled west.

Government forces are surrounding Misrata on all sides but the north, where the city has access to the Mediterranean Sea for supplies and food through Libya's major port. Rebels have beaten back several government attempts to retake the city.

The Gadhafi forces are pushing back on rebel forces trying to break out of Misrata to the west toward Tripoli, where Gadhafi is increasingly cornered under NATO bombardment in the capital.

A rebel fighter in Misrata who identifies himself only as Abdel-Salem said Gadhafi's sons, Khamis and al-Moatassem, and top aid Abdullah al-Senoussi are in command of the operation in Zlitan, about 15 kilometres from Dafinya. They are dug in trying to stop the rebel advance out of Misrata.

"The situation is very bad there. Gadhafi sent huge forces to Zlitan to fortify the city because he knows that if Zlitan falls in the hands of the rebels, the way to Tripoli will be wide open," Abdel-Salam said. "Now the ball is in the court of NATO, but we have not seen any NATO planes flying over despite the fierce battle."

According to Abdel-Salam, a bulk of Zlitan residents are Ghadafi loyalists.

U.S. Sen. Carl Levin spoke of the degredation of Gadhafi's forces Friday after a classified briefing by senior Pentagon officials in Washington. The chairman of the Senate Armed Services Committee said Gadhafi's military and political standing had been weakened by NATO air attacks.

Levin said administration officials offered no predictions on how long the war would last or when Gadhafi might go. He said NATO helicopters, likely British and French, have been taking out tanks without collateral damage.

In Norway, meanwhile, military officials said on Friday the country would scale down its fighter jet contribution the NATO force flying above Libya from six to four planes and withdraw completely from the NATO-led operation by Aug. 1.

The Dutch government, however, has continue its forces' role in the NATO campaign through the end of the three month extension the alliance announced last week. It also plans to contribute a handful of new staff.

U.S. Defence Secretary Robert Gates has urged NATO allies, including the Netherlands, to do more in Libya to share the burden with France and Britain, which are carrying out most of the air strikes.

The Dutch government still will not allow its six F-16 fighter jets involved in the mission to carry out airstrikes. Instead they will continue to enforce the no-fly-zone above Libya.

In addition, the government announced it will send experts in psychological operations and legal affairs to join the mission.