Two Dutch UN peacekeepers have reportedly been killed and one seriously wounded in an explosion during a training exercise in northwest Mali, the Dutch defence ministry said.

"During the accident, two of our men lost their lives," The Netherlands' Vice Chief of Defence Rob Bauer announced after the incident in the town of Kidal on Wednesday.

Another 23-year-old soldier was seriously wounded, and was operated on in a field hospital and then taken to a military hospital in northern Gao, he said.

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The defence ministry named the two men as Corporal Kevin Roggeveld, 24, and Sergeant Henry Hoving, 29.

Officials with the UN mission in Mali said in a statement that "an accidental explosion of a shell caused the deaths of two MINUSMA peacekeepers during a training exercise" in Kidal.

MINUSMA has launched an internal investigation, while Bauer said: "We do not know exactly what happened and we don't want to speculate."

The Netherlands has been taking part in the UN stabilisation mission in the West African nation since April 2014, and has deployed some 400 troops, four Apache helicopters and three Chinooks, the Dutch news agency ANP said.

There are an estimated 12,000 UN troops in Mali. 

The UN mission was deployed in Mali in July 2013 as part of an international effort against armed groups, which overran the country's northern territory.

The north continues to be beset by violence, having fallen under the control of Tuareg-led rebels and groups linked to al-Qaeda in 2012.

Armed groups sidelined the rebels to take sole control, and although they were largely ousted by a French-led military operation in January 2013, they still pose a threat.

The UN Security Council last month decided to send 2,500 extra peacekeepers to Mali, authorising the force to take "all necessary means" to deter attacks in what has become the UN's deadliest mission.

Source: Agencies