Cairo - Al-Qaeda leader Osama Bin Laden called on Somali militants to topple the new president Sheikh Sharif Sheikh Ahmed and to continue fighting "infidels," according to a new audio tape carried by Islamist web sites on Thursday.

The tape, entitled "Fight on, champions of Somalia" and dedicated to "my patient, persevering Muslim brothers in Mujahid Somalia" is produced by al-Qaeda's al-Sahab media-production house. The audio was released as a video showing a still photo of Bin Laden and English subtitles.

It is the reclusive al-Qaeda's third taped message of 2009 - compared with four for the whole of last year.

It is the first time Bin Laden has addressed the general Muslim population of Somalia, although he has previously sent a message to the Somali mujahideen.

Bin Laden accused Somalia's new president of apostasy for splitting from the Islamic Courts Union and joining a coalition government. The Islamic Courts Union controlled southern Somalia until Ethiopian troops, backed by US forces, invaded Somalia in 2006.

Bin Laden said that Sheikh Ahmed, and other "surrogates of our enemies," have no authority, and must be "dethroned and fought."

In January, Bin Laden's deputy, Ayman al-Zawahri, also urged militant Islamists in Somalia to continue fighting along with Palestinians and al-Qaeda cells in Yemen.

The tape is the second from Bin Laden in a week. On Saturday he released a tape accusing some Arab leaders of complicity in Israel's 22-day offensive in Gaza in late December and early January.