Khorasan leader Muhsin al-Fadhli is rumored to have died from the airstrikes mounted by the U.S.-led campaign against terror groups in Syria, the SITE (Search for International Terrorist Entities) monitoring group announced Sunday.

Messages of condolences posted on Twitter allegedly confirmed the death of al-Fadli, also known as Abu Asmaa al-Jazrawi and Abu Asmaa al-Kuwati, a former associate of Osama bin Laden and a high-level al-Qaeda operative, said SITE.

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The tweets made by a Khorasan militant also referred to the death of another Khorasan group leader named Abu Youssef al-Turki. No photos showing the militants' bodies were posted online, Sydney Morning Herald reported.

Reuters said the Syrian airstrikes on September 23 took the terrorists down, but deputy White House national security adviser, Tony Blinken, has not officially confirmed his death.

U.S. officials are trying to make sure he is not faking his death to go underground, Blinken said. He added, however, that there are evidences confirming the Kuwait-born terrorist was dead.

SITE also confirmed that the Twitter messages, dated September 27, 2014, bemoaned the situation in Syria after the United States and its Arab allies mounted a series of aerial bombardments targeting the Islamic State group stronghold in Raqqa.

The strikes also hit Khorasan group targets, which until recently was unknown, but Washington has claimed an imminent security threat to the West.

The Khorasan terror group is an offshoot of the al-Qaeda network and has long been watched by U.S. intelligence agencies, Reuters said.

U.S. officials described Khorasan as a network of seasoned terrorists who had combat experience in Pakistan and Afghanistan. It also has close ties with the Nusra Front, the Syrian wing of the al-Qaeda network.

Khorasan group was established after the United States killed Osama bin Laden, a U.S. official speaking on condition of anonymity told the Sydney Morning Herald.

Last week, the White House expanded its air campaign against the Islamic State, which for weeks had been limited to targets across Iraq. Five Arab countries joined in the first waves of attacks in Syria including the United Arab Emirates, Saudi Arabia and Qatar, but not the strikes against the Khorasan group.

SITE has not confirmed the militant who owned the Twitter account that confirmed the Khorasan leader's death. 

TagsKhorasan group, Khorasan leader Musin al-Fadli, site, Al-qaeda