The Gulf state of Kuwait on Friday urged a halt in Syria's deadly crackdown on pro-democracy protesters and called for dialogue and "true reforms" to end the crisis.

"The state of Kuwait expresses its extreme pain for the continued bloodshed among the brotherly Syrian people," said a statement by a foreign ministry official cited by state news agency KUNA.

Libya's rebel forces on Friday said a NATO strike killed Moammer Gadhafi's youngest son Khamis and 31 others in the disputed town of Zliten, in what would be a severe setback for Tripoli's military leadership.

The claim was denied by government spokesman Mussa Ibrahim, who said "the news about the killing of Khamis by a NATO air strike are very dirty lies to cover the murder of civilians in the peaceful city."

Israeli police deployed in force in Jerusalem's Old City after limiting access to the al-Aqsa mosque compound ahead of the first Friday prayers during Ramadan.

"More than 2,000 police and border guards were deployed in Jerusalem," said a police spokesman, adding access was blocked to the esplanade for Muslim men under the age of 45.

The Obama administration sent its ambassador back to Damascus on Thursday as it incrementally turned up the heat on Syrian President Bashar Assad with tougher rhetoric and new sanctions.

The White House said Assad's deadly crackdown on protesters had put Syria and the Middle East on a "very dangerous path," as Washington extended a raft of recent sanctions to include a businessman close to Assad and his family.

NATO warplanes bombed the Libyan capital early Friday, state television said, as Moammar Gadhafi's regime accused rebels of sabotaging a key pipeline feeding the country's sole functioning refinery.

About 10 loud explosions rocked the city around 1:30 am (11:30 GMT), an Agence France Presse journalist said.

The United States on Thursday stepped up the pressure on Syria over its crackdown on pro-democracy protesters, imposing sanctions on a businessman close to President Bashar al-Assad and his family.

The move freezes the U.S. assets of Mohammed Hamsho and his company, Hamsho International Group, and prohibits U.S. entities from engaging in any business dealings with them, the Treasury Department said in a statement.

At least 109 people were killed on Thursday in and around the Syrian flashpoint protest city of Hama, CNN quoted a global activist group as saying.

"The brutality continues in Hama on the fourth day of Ramadan. Communication with the city and surrounding area is very difficult as the electricity supply has been cut off," the Avaaz non-governmental organization said.

Field Marshal Hussein Tantawi, Egypt's military ruler, will most likely testify in the trial of former president Hosni Mubarak if summoned after a request by the defense, a security official said Thursday.

Fareed al-Deeb, who represented the fallen dictator at his murder trial, asked the judge in its first session on Wednesday to summon Tantawi and military chief of staff Sami Enan along with some 1,600 witnesses.

The United States warned Thursday that President Bashar al-Assad had put Syria and the Middle East on a "very dangerous path," again toughening rhetoric on a crackdown by Damascus.

Washington appears to be moving towards a first direct call for Assad to go, a step it has so far resisted, and is preparing a new round of sanctions against his regime after an escalation of violence in the revolt hub of Hama.

EU foreign policy chief Catherine Ashton on Thursday dubbed Syria's multi-party reform offer "a step in the right direction" but on condition it be put into effect.

"We are still waiting for previously announced reforms to be implemented," Ashton said in a statement issued after President Bashar al-Assad issued a decree allowing opposition political parties.