Basra: Heavy fighting broke out on Tuesday in Iraq's southern city of Basra, where Iraqi authorities have clashed with members of the Mehdi Army militia.

An Iraqi military official said Iraqi forces had launched operations to "cleanse" Basra of armed groups.

"Sounds of explosions were heard in different areas of Basra and columns of smoke have been rising from northern districts of the city," a witness said.

A spokesman for the British forces said troop reinforcements had been sent from across Iraq and that the Iraqi prime minister was in the city to oversee the operation.

Basra hospital has begun to admit casualities, but it is unclear yet if there are any fatalities.