Osama bin Laden, left, sits with Ayman al-Zawahiri, the network's new head [Getty]

Al-Qaeda has released a video message in which Ayman al-Zawahiri, the group's leader, heaps praise on his predecessor Osama bin Laden for his "superior morals" and loyalty to his comrades.

"Days with the imam, Part One", the half-hour tape released on Wednesday, described the network's founder as noble, generous and good.

"I had the honour of the companionship of that man for long periods in travel and in different circumstances," said Zawahiri, an Egyptian who met bin Laden in Pakistan in the mid-1980s when both were supporting guerrillas fighting Soviet forces in Afghanistan.

"People don't know that this man was tender, gentle, kind, with refined feelings, even when life was hard."

Zawahiri became the leader of al-Qaeda in June after bin Laden was killed in a US raid on his secret compound in Pakistan.

"Sheikh Osama would feel great sadness if he felt that his brothers in the path of jihad had been oppressed or had not reached their rightful goal," said Zawahiri.

"That man was very loyal to his brothers and he was intent on remembering them in virtue and praising their way."

Zawahiri was bin Laden's lieutenant and the alleged brains behind much of al-Qaeda's strategy for many years.

"He used to remember the 19 [people] who attacked the idiot of the age, America, in the Pentagon, the seat of its military leadership, and in New York, the symbol of its economic power," said Zawahiri, referring to al-Qaeda's September 2001 hijacked aircraft attacks on the World Trade Center and the Pentagon.

Zawahiri ended by saying that the video would be followed by others about bin Laden. It was not clear when the video was recorded.