Two United Nations peacekeepers from Tanzania were killed, 13 wounded and four were missing in eastern Democratic Republic of Congo on Tuesday when their patrol was ambushed by suspected Ugandan Islamist rebels, the United Nations said.

The peacekeepers were attacked in the village of Kikiki, around 50 km (30 miles) north of the town of Beni in North Kivu province, Felix Basse, spokesman for the mission known as MONUSCO, told Reuters

The Congolese army said earlier on Tuesday it had killed 16 Ugandan Allied Democratic Forces (ADF) rebels during fierce fighting in the same zone over the weekend.

U.N. Secretary-General Ban Ki-moon condemned the attack on the peacekeepers, which occurred as the mission was "carrying out its protection of civilians mandate". His spokesman confirmed the number of dead, wounded and missing.

"The U.N. remains committed to taking all necessary actions ... to protect civilians and neutralize armed groups in eastern (Congo)," Ban's spokesman said in a statement.

He said Ban condemned "the continuing atrocities perpetrated by the ADF against defenceless civilians in the Beni area".

Tuesday's ambush was the second attack on U.N. forces in the area in 48 hours after a MONUSCO helicopter carrying the mission's military chief was fired upon by unidentified gunmen on Monday.

"I won't tolerate any more of these repeated attacks against blue helmets in Beni territory," Martin Kobler, head of MONUSCO, tweeted following the attack. "MONUSCO will carry out robust offensive operations."

Congolese forces launched Operation Sukola I early last year against the Islamist ADF, who are accused of massacring some 300 villagers near Beni between October and December. MONUSCO is providing support for the offensive.

Eastern Congo, where a 1998-2003 conflict resulted in millions of deaths, remains plagued by dozens of armed groups that prey on the local population and exploit the region's vast reserves of gold, tin and diamonds.