Fourteen peacekeepers have been killed and at least 53 have been wounded in an attack on a UN mission base in the eastern Democratic Republic of the Congo, the UN has said.

At least five Congolese soldiers were also killed in Thursday's attack in North Kivu province, United Nations spokesman Farhan Haq said.

UN Secretary-General Antonio Guterres says the attack on peacekeepers in Congo is the worst in the UN's recent history and is 'a war crime'.

Fourteen peacekeepers and five Congolese soldiers have been killed in an attack on a UN mission base in the eastern Democratic Republic of the Congo. At least 53 other peacekeepers were injured (file photo)

'Today is a very tragic day for the U.N. family,' he said, while expressing 'outrage and utter heartbreak'.

He added: 'I condemn this attack unequivocally. These deliberate attacks against UN peacekeepers are unacceptable and constitute a war crime.

'I call on the DRC authorities to investigate this incident and swiftly bring the perpetrators to justice. There must be no impunity for such assaults, here or anywhere else.'

He said early indications are that at least 12 Tanzanian peacekeepers were killed and four of the more than 50 injured are injured critically.

'I condemn this attack unequivocally,' he said. 'These deliberate attacks on peacekeepers are unacceptable and constitute a war crime.'

He urged Congolese authorities to swiftly investigate and bring the perpetrators to justice.

North Kivu province has remained a hotbed of armed militias, who continue to battle for control over the mineral-rich countryside despite the end of a major war over a decade and a half ago.

'It's a very huge attack, certainly the worst in recent memory,' Haq said, adding that the peacekeepers are mainly from the Tanzanian contingent.

North Kivu province has remained a hotbed of armed militias, who continue to battle for control over the mineral-rich countryside despite the end of a major war over a decade and a half ago

Peacekeepers had repelled an attack by fighters with the Allied Democratic Forces rebel group on a UN base in the Beni area, reported Radio Okapi, which is linked to the peacekeeping mission known as MONUSCO.

The base is home to the peacekeeping mission's rapid intervention force, which has a rare mandate to go on the offensive.

The radio station, citing military sources, said fighting lasted four hours. It reported that Congolese forces did not intervene because the closest ones were several miles away.

The mission said it was coordinating a joint response with the Congolese army as well as medical evacuations of the wounded from the base in North Kivu's Beni territory

UN Peacekeeping chief Jean-Pierre Lacroix said he is 'outraged' by the attack.

'Our thoughts and prayers with families and our colleagues in MONUSCO (peacekeeping mission). Reinforcements are on scene and medical evacuations by mission ongoing,' Lacroix, Under-Secretary-General for Peacekeeping, wrote.

Gilbert Kambale, the president of an activist group in Beni, said the attack occurred about 50 km (30 miles) northeast of Beni city on the road that leads to the Uganda border, near where militants killed at least 26 people in an ambush in October.

Nearly 300 peacekeepers have been killed since the UNmission arrived in 1999, according to U.N. peacekeeping data.

Congo, a country the size of Western Europe, has seen immeasurable cruelty and greed as a result of its vast mineral resources.

Peacekeepers had repelled an attack by fighters with the Allied Democratic Forces rebel group on a UN base in the Beni area, reported Radio Okapi, which is linked to the peacekeeping mission known as MONUSCO (file photo)

The nation suffered through one of the most brutal colonial reigns ever known before undergoing decades of corrupt dictatorship. Back-to-back civil wars later drew in a number of neighboring countries.

The conflicts have been numerous since the UN mission's arrival.

Many rebel groups have come and gone, at times invading the regional capital, Goma. One of the greatest threats in the region now comes from the ADF.

The rebel movement has been active since the 1990s but intensified its attacks inside Congo several years ago. Human rights groups say at least 1,000 people have been killed in the last three years.

While the group's members are mainly Muslim, experts say there are no proven links between the ADF rebels and other extremist organizations in Africa.

The ADF rebels once aimed to overthrow President Yoweri Museveni's regime in neighboring Uganda. By the 1990s, the fighters had established themselves in Congo.

The UN mission in 2006 helped carry out Congo's first free and fair elections in 46 years, but since then the winner of that vote, President Joseph Kabila, has become further entrenched in his post. Anger has grown as presidential elections originally set for late last year have been repeatedly delayed.

Established in 2010, MONUSCO, the United Nations's largest peacekeeping mission, has recorded 93 fatalities of military, police and civilian personnel.

The UN peacekeeping mission in Congo is the largest and most expensive in the world and is aimed at calming a number of armed groups in the vast, mineral-rich Central African nation.