Al Qaeda says its No. 3 man and commander of its operations in Afghanistan has died, according to a group that monitors Islamist websites.

Al Qaeda announced the death of Mustafa Abu Yazid in a message posted on such websites Monday, the Maryland-based SITE Intelligence Group said. While the message didn’t detail the circumstances of Yazid’s death, it did say his wife, three of his daughters, a granddaughter and others were killed, according to SITE.

Yazid, an Egyptian national, is believed to have been a financial manager for al Qaeda, as well as a co-founder of the terrorist group, according to SITE.

A U.S. official speaking on condition of anonymity said the government has “strong reason to believe” that Yazid was killed recently in Pakistan’s tribal areas.

“In terms of counter-terrorism, this would be a big victory,” the official said, noting that Yazid was al Qaeda’s prime conduit to leader Osama bin Laden and his deputy, Ayman al-Zawahiri.

U.S. intelligence officials say he would brief would-be al Qaeda operatives who came from the United States for attacks abroad.

In the past, Yazid has made numerous statements on jihadist websites and in video releases from al Qaeda’s media arm, al Sahab.

Most recently, he announced that al Qaeda took responsibility for a December 30 attack on a base in eastern Afghanistan that killed seven CIA officers and consultants and a Jordanian army captain. He said the attack avenged the death of Baitullah Mehsud, leader of the Taliban in Pakistan who was killed in a missile strike last August, and al Qaeda operatives Saleh al-Somali and Abdullah al-Libi.

IntelCenter, a think tank that tracks terrorist groups, said Yazid’s death was one of the most significant blows against al Qaeda in recent years.

But IntelCenter added that al Qaeda knows losses are inevitable and plans for them.

“While the loss of al-Yazid will have an impact, the group will likely maintain its operational tempo in terms of attacks and other activities,” IntelCenter said in a statement.

(Source: CNN)