Mali's Tuareg rebels took over the northern town of Menaka Wednesday after the government forces stationed there pulled out overnight, officials and witnesses said.

"The Malian army contingent that was in Menaka left the town overnight. Around 40 armed rebels entered it in the afternoon," a local official said on condition of anonymity.

He said no violence was reported but added that residents were leaving the town, located near the border with Niger.

"The town is emptying," one resident also told AFP by phone.

A military official in the northeastern city of Gao said the pullback was a tactical move while another army source said government forces were concentrating their efforts on larger towns.

"It appears that the strategy is to beef up larger urban areas and using them as launchpads for attacks and reprisals using helicopters or ground troops," a Bamako-based military expert explained.

Menaka was the first town attacked by rebels from the Azawad National Liberation Movement (MNLA) on January 17. The rebels have since attacked towns near the borders with Algeria and Mauritania.

The ongoing offensive is the largest since 2009 by Tuareg rebels, whose ranks have been boosted by the recent return of men who fought in Libya alongside Moamer Kadhafi.

The UN Office for the Coordination of Humanitarian Affairs in Niamey said Wednesday that around 1,000 people, including 30 members of the military, had fled northern Mali in recent days and found refuge in neighbouring Niger.