Two suicide bombers killed a senior al-Qaeda operative on Sunday, blowing themselves up inside the militant leader's compound in the northern Syrian city of Aleppo, rebels and activists said.

Abu Khaled al-Suri was the representative of al-Qaeda chief Ayman al-Zawahri in Syria, rebels said. He was also a co-founder of Ahrar al-Sham, a powerful, hard-line Syrian rebel group seeking the overthrow of President Bashar Assad. The group, alongside other Syrian rebel brigades, has been embroiled in infighting against a breakaway al-Qaeda group, the Islamic State of Iraq and the Levant.

"Sheik Abu Khaled al-Suri was the biggest figure in global jihad," said Akram al-Halabi, spokesman for the Islamic Front, a loose coalition of Islamic-oriented rebel groups, including Ahrar al-Sham. "He was appointed by Sheik Ayman al-Zawahri to mediate," al-Halabi said, speaking to The Associated Press via Skype.

New complication

Al-Souri's killing will further complicate efforts to resolve weeks of infighting between rebels and militants of the breakaway al-Qaeda group, the Islamic State in Iraq and the Levant. The fighting has killed thousands since January. It has also badly weakened rebel ranks, allowing Assad-loyal forces to advance into key-rebel areas, including around Aleppo.

Rebels believe the Islamic State was behind the bombing that killed al-Suri, al-Halabi said. Weeks ago, he wrote a letter criticizing the rogue al-Qaeda group, al-Halabi added.

"The first fingers of blame point to The State," said al-Halabi. "Unfortunately this is going to make the infighting worse."

'Sheik Abu Khaled al-Suri was the biggest figure in global jihad.' - Akram al-Halabi, spokesman for the Islamic Front

The Britain-based Syrian Observatory for Human Rights said two others were killed in the attack, which it attributed to the Islamic State. The Observatory obtains its information from a network of activists on the ground.

Al-Souri's activities in Syria were a chief reason why the United States and other Western allies held back on providing heavy weapons to rebels seeking Assad's overthrow, said analyst Charles Lister. Al-Souri'spresence in Ahrar al-Sham nearly led the U.S. to declare it a terrorist group.

"He is essentially a core al-Qaeda veteran who almost certainly … had extensive, close relations with [Osama] bin Laden," and other senior leaders, Lister said. "The fact that he had such a high position in Ahrar al-Sham, and confirmed it himself, his al-Qaeda history — it made elements in the U.S. administration potentially consider Ahrar al-Sham as a terrorist organization."

In 2002, Spanish officials described al-Suri, whose real name is Mohamed Bahaiah, as bin Laden's courier between Afghanistan and Europe.

Also Sunday, a car bomb exploded near a charity field hospital close to the Turkish border, killing one person and wounding medics and patients who had fled violence elsewhere in the country, activists and Turkish media said.