Five people were seriously injured in fighting between Tuareg and Islamist rebels in northern Mali Wednesday, officials said.

Oumar Sall of the Timbuktu Islamic Council said the clashes broke out as Tuareg of the National Movement for the Liberation of Azawad (MNLA) attempted to pass a checkpoint manned by fighters from the Islamist Ansar Dine (Defenders of Faith).

"The people from MNLA wanted to pass but Ansar Dine refused and then the clash took place," he told AFP.

A nurse at the main hospital in Timbuktu, Oumar Ould Sidy Ibrahim, said five people were seriously injured, four of them from the MNLA and one from Ansar Dine. This was confirmed by a police source.

The two rebel groups with different ideologieshave had an uneasy relationship since occupying the north of Mali after a coup in Bamako in March.

Tensions have risen over efforts to merge and form a breakaway state, which remain deadlocked as the parties fail to agree on the implementation of strict Islamic law.

Ansar Dine, which is backed by Al-Qaeda in the Islamic Maghreb and has the upper hand, says the implementation of sharia is non-negotiable.

The fighters clashed last week in the first serious confrontation between the two groups, after several protests by residents of northern towns against Ansar Dine and in support of the MNLA.