WASHINGTON, June 1 (Xinhua) -- The White House on Tuesday welcomed the death of Mustafa Abu al-Yazid, the Al-Qaeda number three leader, saying it was "unquestionably a severe blow" to the terrorist organization.

"We welcome his demise," said White House spokesman Robert Gibbs, adding that his death was "unquestionably a severe blow" to the organization.

Al-Yazid is one of the founding members of Al-Qaida and is believed to have financed the attackers who flew two planes into World Trade Center on September 11, 2001.

Al-Qaeda reportedly announced Monday that al-Yazid had been killed along with members of his family. A U.S. official said he was believed to have been killed in a U.S. unmanned drone attack in the Pakistan-Afghanistan border area.