Thousands of Central African Republic (CAR) refugees are threatened by malnutrition in northeastern Democratic Republic of Congo where they have sought refuge, a medical charity said Thursday.

CAR is struggling to recover from the coup that ousted president Francois Bozize in March 2013 and triggered a wave of deadly sectarian violence between the country's Christian and Muslim populations.

Surging violence in the Central African Republic has forced tens of thousands to flee their homes in recent weeks to escape killings, rape and pillaging by militias, the United Nations said Tuesday.

Since the beginning of the year, some 30,000 people have left their homes and found refuge within CAR, while more than 20,000 others have flooded into neighboring Democratic Republic of Congo since December, the U.N. refugee agency UNHCR said.

Foreign soldiers killed seven former rebels of the mainly Muslim Seleka and arrested some 20 others in Bria in the Central African Republic, the United Nations said in a statement.

"The toll was seven dead, nine wounded and about 20 arrested from the ex-Seleka, while there were no victims among the international forces," the U.N. mission in CAR (MINUSCA) said in the communique obtained by AFP late Wednesday.

U.N. chief Ban Ki-moon is seeking to boost the U.N. force in the Central African Republic by 1,030 peacekeepers as the country prepares for elections, according to a letter released Thursday.

Ban asked the Security Council in the letter to authorize the additional 750 military personnel and 280 police for MINUSCA, which stands at about 8,600.

Militia forces in war-torn Central African Republic appealed Friday for international support for an ceasefire agreement struck without government involvement.

The deal was signed last week in Kenya between senior representatives of the anti-balaka rebels and the ex-Seleka movement of ex-president Michel Djotodia.

Armed men on Sunday kidnapped the Central African Republic minister for sport and young people and former rebel chief Armel Ningatoloum Sayo as he returned from church in the capital Bangui, his wife said.

The kidnapping is the first of a member of the government, though comes amid a spate of abductions in the city in the last week. 

A French aid worker kidnapped on Monday in the Central African Republic by the anti-balaka militia has been freed, France's Foreign Minister Laurent Fabius said Friday. 

"Our compatriot Claudia Priest, who was kidnapped at the start of the week in the Central African Republic, is finally free. It's an immense relief for all those who have worked towards this happy outcome," Fabius said in a statement.

U.N. rights investigators said Wednesday that an international tribunal should be set up to try cases of atrocities in the Central African Republic but that donor countries were unwilling to fund it.

The recommendation followed a commission of inquiry report released this month that concluded that war crimes and crimes against humanity were committed over the past two years in the CAR.

A Ugandan commander of the notorious Lord's Resistance Army arrived at the International Criminal Court detention center in The Hague on Wednesday to face war crimes charges.

His detention means the world is "one step closer to ending the LRA's reign of terror in the African Great Lakes region," the court's chief prosecutor Fatou Bensouda said.

A commander of the notorious Lord's Resistance Army who surrendered last week is on his way to the International Criminal Court in The Hague, a spokesman for the court said Tuesday.

Dominic Ongwen is one of the main leaders of the Uganda rebels who are accused of killing more than 100,000 people in a bloody rebellion that started in 1986.