The U.N. humanitarian chief started a mission to Syria on Wednesday to urge the regime to allow aid into battered protest cities, putting the focus on civilians in a conflict which has cost thousands of lives.

Valerie Amos flew in for a two-day visit, after an international outcry over President Bashar al-Assad's previous refusal to let her in, and is to followed by U.N.-Arab League envoy Kofi Annan on Saturday.

Air France on Wednesday said it had cancelled its Paris-Damascus service "until further notice" because of unrest linked to ongoing protests against Syrian President Bashar Assad's regime.

"Because of the situation in Syria, Air France has decided to suspend its flights to Damascus until further notice," a spokesman said, after the airline had already cancelled two flights to Damascus earlier in the week.

Tanks and troop carriers were headed for Syria's embattled northwestern province of Idlib on Wednesday, said the Syrian National Council, the main opposition alliance.

"The SNC has noted 42 tanks and 131 troop carriers leaving Latakia in the direction of the town of Saraqeb," in Idlib province, "as well as military columns heading for the town of Idlib," the group said in a statement.

Egypt's Foreign Minister Mohammed Amr has warned that arming rebel fighters in Syria would lead to a civil war, his ministry said on Wednesday.

Arming the ill-equipped rebels, mainly Syrian army defectors, would "lead to an escalation in the military conflict and spark a civil war in Syria", Amr said, according to a statement issued by his ministry.

Libyan leader Mustapha Abdel Jalil on Wednesday said he would defend national unity "with force" if necessary, after tribal leaders and a political faction declared autonomy for an eastern region.

"We are not prepared to divide Libya," Abdel Jalil said as he called on leaders in the eastern Cyrenaica region to engage in dialogue and warned them against remnants of the regime of slain leader Moammar Gadhafi in their ranks.

Israeli troops entered the northern Gaza Strip on Wednesday morning, sealing the Erez border crossing between the territory and Israel, Hamas officials said.

"Occupation forces moved into the northern Gaza Strip and began bulldozing work and closed the Erez crossing to travellers," a statement from the Hamas interior ministry said.

Israel welcomes the possible resumption of international talks on Iran's nuclear program, but it must prepare for the chance they will fail, Israel's national Security Council chief said Wednesday.

"I am very happy about the resumption of talks between Iran and the big powers, particularly if it results in Iran abandoning its nuclear program. But we must prepare for their failure," Yaakov Amidror told Israeli public radio.

Unknown assailants have shot dead a Yemeni policeman and wounded four others in the country's restive south, a security official said on Wednesday, the fourth such attack in less than a week.

"The gunmen opened fire on a police checkpoint killing one policeman and wounding four others," late Tuesday in the city of Ataq, the capital of Shabwa province, an al-Qaida stronghold, the official told Agence France Presse.

U.S. President Barack Obama Tuesday described the violence in Syria as "heartbreaking," but cautioned there was no simple solution, warning unilateral military action would be a mistake.

"What's happening in Syria is heartbreaking, and outrageous, and what you've seen is the international community mobilize against the Assad regime," Obama told a White House press conference.

Secretly filmed footage shown by a British TV station shows what the report said was evidence of patients being tortured in a military hospital in the battered Syrian city of Homs.

Images broadcast by Channel 4 on Monday show bandaged patients chained to hospital beds by their ankles, while a whip and electrical cable lie nearby.