The leader of al-Qaida confirmed the death of the group's second-in-command, who was killed in a U.S. drone strike in northwestern Pakistan in June.

In a video posted late Monday on militant websites, al-Qaida chief Ayman al-Zawahri described his late lieutenant Abu Yahya al-Libi as a "lion of jihad and knowledge."

The killing of al-Libi, who was Libyan by birth, was the biggest setback to al-Qaida since the death of Osama bin Laden.

Al-Zawahri also urged Libyans — al-Libi was born in the north African country — to attack Americans to avenge the late militant's death, saying his "blood is calling, urging and inciting you to fight and kill the Crusaders."

Al-Libi, whose real name was Hassan Mohammed Qaid, was considered a media-savvy and charismatic leader with religious credentials. He rose to prominence in the group after escaping from the U.S. military prison at the Bagram Air Base in Afghanistan in 2005.

In his eulogy, al-Zawahri also recalled how al-Libi fought in Afghanistan against the Soviet Union in the 1980s and then against the U.S. after the American-led invasion following the Sept. 11, 2001, attacks. He also praised al-Libi's writings, saying he fought the West "with his hand, pen and tongue."