The leader of al-Qaida has called for holy war against the United States and Israel over an anti-Islamic video which triggered mayhem in the Muslim world.

Ayman al-Zawahiri praised as demonstrators who breached the US embassy in Cairo and the attackers who stormed the US consulate in Benghazi last month in violence linked to the film as "honest and zealous".

The Benghazi attack on 11 September, in which the US ambassador to Libya, Chris Stevens, and three others were killed, is now believed to have been carried out by al-Qaida-linked militants.

The trailer for the film produced by Nakoula Basseley Nakoula, a California-based Egyptian-American angry at the treatment of Christians in his homeland, triggered mayhem across the Muslim world after it was uploaded to YouTube, with at least 17 people killed in violent protests.

In an audio message released by al-Qaida's media arm As-Sahab and posted on militant websites on Saturday, al-Zawahiri claimed Washington had allowed the film's production under the pretext of freedom of expression, "but this freedom did not prevent them from torturing Muslim prisoners".

Nakoula, 55, had been previously convicted of bank fraud before he embarked on making a film under the assumed name of Sam Bacile. The Innocence of Muslims depicts the prophet Muhammad in an extremely negative light, which inflamed many Muslims around the world and gave others the pretext for violence.

There are unconfirmed reports the film was screened once earlier this year to a largely empty cinema in Hollywood. Not in question is the fact that in July a 13-minute video in English purporting to be a trailer for a full-length film was posted on YouTube under the pseudonym Sam Bacile.

It was subsequently promoted by a Washington DC-based radical Coptic activist, Morris Sadik, and the Qur'an-burning Florida pastor Terry Jones. An Arabic-language version was posted on YouTube on 4 September. Five days later it was denounced by media and Muslim clerics in Egypt, prompting the assaults on US diplomatic missions.