Updated

The Latest on deadly attack on U.N. peacekeepers in Congo (all times local):

4:55 p.m.

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

"Today is a very tragic day for the U.N. family," the U.N. chief says.

Guterres is expressing "my outrage and utter heartbreak" at Thursday night's attack, saying early indications are that at least 12 Tanzanian peacekeepers were killed and at least 40 injured, four critically. He says at least five Congolese soldiers were also killed.

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

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

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4:05 p.m.

A United Nations spokesman says 14 peacekeepers have been killed and over 40 wounded in an attack in eastern Congo.

Deputy spokesman Farhan Haq says at least five Congolese soldiers were also killed in the attack in North Kivu province.

Haq says the peacekeepers are mainly from the Tanzanian contingent.

"It's a very huge attack, certainly the worst in recent memory," Haq says.

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3:30 p.m.

A "large number" of United Nations peacekeepers have been killed and wounded in an attack in eastern Congo, the U.N. peacekeeping chief said Friday.

Jean-Pierre Lacroix said he was "outraged" by the attack Thursday evening in North Kivu province. He said on Twitter that medical evacuations were ongoing from the scene. He did not identify the attackers.

The U.N. 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.

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