Al-Qaeda's franchise in North Africa on Tuesday urged Muslims to storm US embassies and kill American envoys in Muslim countries in protest over a film insulting Islam, a monitoring group said.

"We call on Islam's youths to take after the lions of Benghazi (in Libya) by pulling down America's flags that are flying over all of its embassies in our capitals," said Al-Qaeda in the Islamic Maghreb, according to IntelCenter.

AQIM urged people "to burn them (the flags), to stomp them underfoot, and to kill its (US) ambassadors and representatives or expel them and purge our land of their filth in revenge for the honour of the best of mankind," referring to Islam's Prophet Mohammed.

The jihadist group's written statement was dated September 15, IntelCenter said, a few days after protests began in Muslim countries over a US-produced film deemed insulting to Islam and its prophet.

Attacks in Morocco, Algeria, Tunisia and Mauritania specifically were urged, particularly the cities of Casablanca, Algiers, Tunis and Nouakchott.

The statement evoked last week's attack on the American consulate in Benghazi that killed the US ambassador to Libya, Chris Stevens, and three other Americans.

Suspected Islamic militants fired on the consulate with rocket-propelled grenades and set it ablaze on the anniversary of the September 11, 2001 Al-Qaeda terror attacks on the United States.

A senior US official said that extremists appeared to have used the demonstration against the film as a "pretext" to attack American interests on the anniversary.