State Department Spokesman Matthew Miller said the attacks were "unacceptable" and condemned "such violence and the larger threat posed by armed actors operating" there.

On Monday, the UN peacekeeping mission in Mali, Minusma, said it had been forced to withdraw earlier than usual from the northern town of Ber amid deteriorating security.

It said that its withdrawing forces had been attacked twice, with some of the soldiers injured.

The US State Department says the attacks highlight the threat of worsening violence "and the importance of all Malian parties settling their differences peacefully".

"It is critical that Minusma be permitted to conduct its withdrawal in a safe and orderly manner, and we call on the transition government to cooperate fully until the final Minusma element departs," it adds.