An air strike is believed to have killed at least four leaders including the top frontline commander of the al-Qaeda-affiliate group al-Nusra in Syria.
The extremist group has confirmed Abu Hommam al-Shami was killed along with three others as they were holding a meeting in Syria's northern Idlib province.
Syria's state news agency said the Islamist militants were the target of a special operation carried out by government forces.
Al-Shami was a veteran al-Qaeda jihadist from Damascus and the general military commander of al-Nusra, which is suspected to be in the process of snapping ties with al-Qaeda. He is believed to have operated from several conflict zones including Iraq, Syria and Afghanistan.
There was also speculation that the aerial bombardment was launched by the US-led coalition, which is currently pounding Islamist targets in Iraq and Syria.
"We cannot confirm press reports of the deaths of senior al-Nusra leaders near the province of Idlib. Neither the US nor the coalition have conducted air strikes near that location in recent days," Pentagon spokesperson Colonel Steve Warren said.
The Britain-based Syrian Observatory for Human Rights has confirmed the attack saying many people were killed.
However, there has been no word about al-Nusra's overall leader Abu Mohammad al-Golani.
The al-Nusra front, comprising highly-trained and well-armed fighters, has become a strong force challenging the Syrian regime's troops along with other rebel groups ever since it came into action in 2012.