Ayman al-Zawahri is al-Qaeda's second in command and long considered the group's operational head [GALLO/GETTY]

Ayman al-Zawahiri, al-Qaeda's second in command, has issued a eulogy for Osama bin Laden, saying the slain group's chief terrified the US when he was alive and would continue to do so in death.

Al-Zawahiri appeared in a white Arab robe and turban, a Kalashnikov at his side, in a 28-minute video posted on jihadist online forums on Wednesday.

"We will pursue the jihad until we expel the invaders from Muslim lands," he was quoted as saying in the video titled "The Noble Knight Dismounted".

The Egyptian, who has long been considered al-Qaeda's operational head, heaped praise on bin Laden, killed in a May 2 US raid in Pakistan.

Al-Zawahiri, who is believed to be operating from somewhere near the Pakistan-Afghanistan frontier, also blasted the US for burying bin Laden at sea and urged the Pakistani people to rise against the country's military rulers and politicians, describing them as "traitors".

Marwan Bishara, Al Jazeera's senior political analyst, said al-Zawahiri is an irrelevant figure in today's Arab world.

"The whole idea of being the 'second in command' is of course more of a media construct than it is in any way a chart within that group. Bin laden was the guru and the guru is dead.
 
"What is left is an organisation that claimed a false prophecy during a time that Arabs were lost. That was in the 80s, 90s and the last decade. Now the Arabs have found their voice, and are out in their millions in the streets in the Arab world. So, in a sense, the whole idea of al-Qaeda, even if it had any merits in the eyes of very few, it simply has absolutely no role in today's Arab world," Bishara said.