"We cannot confirm now what new areas al-Shabab have taken," Nour said.

Al-Shabab, a group alleged by US officials to have connections to al-Qaeda, said that its fighters had made progress in northern Mogadishu and forced government troops into retreat.

No exodus

The Somali government denied the movement's claim and announced that at least 70 civilians were killed and more than 200 others injured in the recent fighting.

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Earlier reports claimed that hundreds of people had begun a mass exodus from the capital due to the fighting, but our correspondent reported that this was not the case.

He said that people were moving from one area to another, to escape the fighting, but hundreds of people were not leaving the city as reported.

Al-Shabab has been fighting Somalia's UN-backed government since the start of 2007, launching frequent attacks on its bases in Mogadishu.

Al-Shabab controls much of the capital in a country deprived of an effective central government for nearly two decades.

More than 21,000 Somalis have been killed in fighting since the start of the uprising, 1.5 million have been uprooted from their homes and nearly half a million are sheltering in other countries in the region.