A suicide bomber killed four Chadian United Nations peacekeepers at a military camp in rebel-infested north-eastern Mali on Wednesday, the UN and the government said.

The bomber struck in a car laden with explosives at the entrance to the barracks, which houses local soldiers as well as international troops from the UN's MINUSMA peacekeeping force.

"Today at 3:30pm (1500 GMT), a suicide car exploded at the entrance of the MINUSMA camp... The attack killed four peacekeepers," a statement from the force said.

"In addition, the attack wounded 10 people who are currently being evacuated, including six from MINUSMA and four members of the Malian armed forces."

The statement quoted MINUSMA chief Bert Koenders condemning "this cowardly and odious attack" in Aguelhok, a town of 8,000 in the Ifoghas mountain range.

"I am shocked that brave peacekeepers have again been targeted. This attack will not deter the MINUSMA from its mission of peace and security in Mali," Koenders said.

A Malian military source had earlier said that "at least four Chadian and Malian soldiers" were killed.

But a ministry of defence source told AFP Malians initially thought to be among the dead turned out to have survived and were severely wounded, while the dead were all Chadian.

It was the first major attack in the Kidal region since the government and the three main rebel groups signed a ceasefire deal in May to end days of violence in the northern desert.

Around 50 Chadians have been killed since the country's leader Idriss Deby sent troops to fight Islamist rebels alongside French troops in Mali at the beginning of last year.

Kidal is the cradle of Mali's Tuareg separatist movement, which wants independence for a vast swathe of northern desert it calls "Azawad" and which has launched several rebellions since the 1960s.

- Security challenges 'enormous' -

The country descended into crisis in January 2012, when Tuareg rebels from the National Movement for the Liberation of Azawad launched the latest insurgency.

A subsequent coup in Bamako led to chaos, and militants linked to Al-Qaeda overpowered the Tuareg to seize control of Mali's northern desert.

A French-led military operation launched in January 2013 ousted the extremists, but sporadic attacks by armed Islamists have continued, and the Tuareg demand for autonomy has not been resolved.

The UN has acknowledged that it is struggling to get peacekeeping troops into place in Mali as France seeks to draw down its force battling militant groups.

Almost 18 months after France intervened to halt an Islamist march on Mali's capital, the UN mission in the impoverished west African nation has just 7,250 of the 11,200 troops it intended to build up, according its website.

France is winding down its force from a peak of around 5,000 soldiers but is to keep 1,000 troops in Mali beyond July.

The UN peacekeepers took over security in July last year from a pan-African military mission which had been supporting the French troops.

MINUSMA chief Koenders told the UN Security Council in January the security challenges in Mali are still "enormous".

A roadside bomb struck a UN vehicle in northern Mali in April, wounding a peacekeeper from Guinea during a UN visit of foreign dignitaries.

Two Senegalese peacekeepers were killed six months ago when a car filled with explosives crashed into a bank in Kidal's regional capital -- also called Kidal -- that was being guarded by MINUSMA troops.

A Malian jihadist, Sultan Ould Badi, claimed responsibility for the attack, calling it payback for African countries' military support for French operations on the continent.