WASHINGTON (CNN) – A senior al Qaeda terrorist who allegedly plotted and carried out attacks against U.S. and coalition forces was killed in Pakistan, a knowledgeable Western official and a military source told CNN Thursday.

He was identified as Abu Laith al-Libi, 41, who was on the military’s most wanted list.

Al-Libi was thought to have been involved in the February 2007 bombing at Bagram Air Base in Afghanistan while Vice President Dick Cheney was visiting.

The knowledgeable Western official said al-Libi was "not far below the importance of the top two al Qaeda leaders" — Osama bin Laden and Ayman al-Zawahiri.

CNN Middle East analyst Octavia Nasr called al-Libi the third-ranking terrorist in al Qaeda and fourth in the world.

Terrorist Islamist Web sites acknowledged al-Libi’s death.

"May God have mercy on Sheikh Abu Laith al-Libi and accept him with his brothers, with the martyrs," said a eulogy posted on a main Islamist site, Al-Ekhlaas.

Al-Libi was of Libyan descent and was believed to have been in the Afghan-Pakistani border region, according to the U.S. military.

"May God have mercy on Sheikh Abu Laith al-Libi and accept him with his brothers, with the martyrs," said a eulogy posted on a main Islamist site, Al-Ekhlaas.

Al-Libi was of Libyan descent and was believed to have been in the Afghan-Pakistani border region, according to the U.S. military.

He was a significant, senior al Qaeda figure who had taken on a more prominent role in the organization in recent years, and was responsible for plotting attacks, some of which targeted U.S. and coalition forces as well as Afghan officials, a U.S. counterterrorism official told CNN.

In an earlier role, he was a leader of the Libyan Islamic Fighting Group, which eventually merged with al Qaeda and was responsible for planning attacks throughout North Africa and the Middle East, the counterterrorism official said.

The official described al-Libi as part of al Qaeda’s inner circle, who helped fill the void created by the capture or death of other senior people in the organization.

A U.S. military official with Combined Joint Task Force-82 — the anti-terror unit responsible for searching for al-Libi in Afghanistan — said the unit had no information on al-Libi’s death.

But he added that the task force does not collect information from outside of Afghanistan and would be informed of targeted operations only "if the Pakistani military share(s) that with us."

The Pakistani military said an explosion occurred in North Waziristan on Tuesday, and 12 people were killed.

However, it was unclear whether this was the incident in which al-Libi was killed.

Military spokesman Maj. Gen. Athar Abbas told CNN that it was not clear who attacked whom and that he could not comment on the identities of the dead since local al Qaeda and Taliban associates removed the bodies and buried them.

Al-Libi could have been killed by a missile fired from a drone operated by the CIA and other U.S. government agencies, Starr said. It’s not an operation the U.S. or Pakistan would publicly acknowledge, she added.

The U.S. military placed al-Libi on its most wanted list in 2006, behind bin Laden, al-Zawahiri and Taliban leader Mullah Omar. In October, the U.S. announced rewards ranging from $20,000 to $200,000 for al-Libi and 11 other mid-level Taliban and al Qaeda leaders.

At that time, the military distributed posters and billboards with pictures and names of the insurgents around eastern Afghanistan.

The terrorist appeared in a 2002 audio recording posted on an Islamist Web site, saying al Qaeda had regrouped and intended to expand its war to include assassinations and attacks against infrastructure.

He also appeared in a 2004 video that showed him participating in an attack on an Afghan army base.