The "withdrawal of US forces and assets from Air Base 201 in Agadez is complete," the Pentagon said in a joint statement with Niger's defense ministry.

"This effort... will continue between US and Nigerien armed forces over the coming weeks to ensure the full withdrawal is complete as planned," it continued.

It did not give any detail on what assets the US may still have left to withdraw in the country.

Some 200 soldiers had been at the Agadez drone base, in the north of the country.

US troops were part of an international effort to suppress jihadist forces that regularly strike across the region.

But the Niger military leaders who seized power in a coup a year ago in March told US and French forces to quit the country.

"Over the past decade, US troops have trained Niger's forces and supported partner-led counterterrorism missions against Islamic State and al Qaeda in the region," the statement continued.

"The effective cooperation and communication between the US and Nigerien armed forces ensured that this turnover was finished ahead of schedule and without complications," it said.