WASHINGTON: A new video featuring al Qaeda's number two Abu Yahya al-Libi, who the United States said was killed last week after a drone strike in Pakistan, was posted online Tuesday, monitoring services said.

Both the SITE Monitoring Service and IntelCenter, which keep tabs on jihadi websites, said it was not clear when the video had been made.

The US-based SITE said the video production date only indicated it had been produced by al Qaeda's media arm As-Sahab some time after November 2011.

In the video, Libi - a charismatic figure beloved by rank-and-file radicals - denounces Syrian President Bashar al-Assad as a “tyrant” and calls his government a “criminal regime,” according to SITE's translation.

He urges the Syrian people to continue fighting and calls on fighters in Iraq, Jordan and Turkey “to rise to help their brothers and to sacrifice themselves for them.” Libi also accuses “the West and their agent assistants” of being complicit in the crimes perpetrated by Assad's regime.

SITE said the message post accompanying the video refers to Libi with honorific titles normally reserved for the living.

IntelCenter said: “It is not unknown for groups to release videos of key figures that were filmed prior to their death but had not yet been released.” The crackdown by Assad's regime against a popular uprising began in March 2011 - well before Libi's apparent death in a drone strike in Pakistan's lawless North Waziristan, a hotbed of Taliban and al Qaeda activity.

The United States said last week that Libi was dead, dealing the weightiest blow to the terror group since the killing of Osama bin Laden in May 2011.

Officials refused to confirm the circumstances of Libi's death, but Pakistani authorities previously spoke of a pre-dawn CIA drone strike on a compound in North Waziristan, near the Afghan border.

A trusted lieutenant of bin Laden, Libi appeared in countless al Qaeda videos and was considered the chief architect of its global propaganda machine.