BBC Online :A senior rebel commander linked to al-Qaeda has been killed in a suicide attack in the Syrian city of Aleppo.Abu Khaled al-Suri was among several people who died in the attack on a compound of his militant group, Ahrar al-Sham, activists say.Another militant group, the Islamic State of Iraq and the Levant, known as ISIS, is believed to be responsible.ISIS is engaged in a bloody power struggle with rival factions in the Syrian rebellion.It has been engaged in violent clashes with other rebel groups since early January in which hundreds of fighters have been killed on both sides.Ahrar al-Sham is a prominent, hard-line rebel group, part of a powerful alliance of seven groups known as the Islamic Front. According to rebel and activist sources, the attack was carried out by one suicide bomber – or possibly two – who penetrated its headquarters in Aleppo.Al-Suri was believed to be the main representative in Syria of the global al-Qaeda leader, Ayman al-Zawahiri, who took over after Osama Bin Laden was killed.Al-Suri was reported to have become increasingly critical of ISIS, says the BBC’s Jim Muir in neighbouring Lebanon. His death is thought likely to aggravate further the brutal confrontation between ISIS and the other groups, our correspondent adds. Al-Suri, whose real name is believed to be Muhammad Bahaiah, was a veteran al-Qaeda operative who is reported to have fought the Americans in both Afghanistan and Iraq, and to have worked closely with Osama bin Laden.Also on Sunday, several people were reported killed by a car bomb near a field hospital in northern Syria, close to the border with Turkey.Activists said the blast happened in the rebel-held town of Atmeh, which hosts a camp for thousands of people displaced by Syria’s civil war. It was not immediately clear who had carried out that attack.According to UN figures, 6.5 million Syrians have been displaced by Syria’s civil war and 2.5 million are registered as refugees. Lebanon has taken the highest number of refugees, followed by Jordan and Turkey.