At least 21 people have been killed by machete-wielding assailants during an overnight attack in the Democratic Republic of Congo, an official says.

"They surprised the peasants who were sleeping in their houses," Omar Kavota, a spokesman for the Civil Society of North Kivu, told Reuters on Wednesday. "They killed 14 men and seven women, but this time they spared the young children."

The attack occurred in the northeastern town of Mayangose. It is not clear who was behind the attack.

The U.N. mission in Congo confirmed the attack, but did not give a death toll, Reuters reports.