Spokesman for Democratic Republic of the Congo's army said soldiers and rebels clashed in the Beni province of North Kivu bordering Uganda in the east on Friday.
Four soldiers and at least 13 militia members were killed during clashes in eastern Democratic Republic of the Congo, the army said on Saturday.
The two sides clashed in the Beni province of North Kivu bordering Uganda on Friday, said Lieutenant Anthony Mualushayi, spokesman for the army in the region.
At least another five soldiers were wounded he said, adding that the fighting had been particularly fierce because the enemy forces were concentrated.
While Mualushayi said 14 ADF militia members had been killed in the fighting, another army spokesman, Sylvain Ekenge, put the figure at 13 in comments to the UN's Okapi radio.
The ADF began as a rebel group in Uganda that opposed President Yoweri Museveni.
It then fell back to North Kivu, Congo's border province with Uganda, during the Congo Wars of the 1990s.
The militia appears to have halted raids inside Uganda and its recruits today are of various nationalities.
Already blamed for hundreds of civilian deaths in the Beni region since 2014, the group embarked on a series of massacres after the army launched a crackdown in October.