Nine civilians were killed in the restive eastern DR Congo after they were kidnapped by an Islamist militia group, local officials said on Sunday.

The Allied Democratic Forces militia or ADF has been blamed for killing around 500 people in retaliation for an army crackdown on their bases in the forests around the Beni region.

The nine victims' bodies were found in the province of North Kivu, which borders Rwanda, regional administrator Donat Kibwana said.

"These victims were hostages kidnapped on Friday by the ADF," the local official said.

In another incident on Saturday in Fizi, in neighbouring South Kivu province, militia gunmen attacked an army unit, killing two soldiers, a local army spokesman said.

Dozens of militia groups operate in eastern DR Congo, a legacy of the two Congo wars in the 1990s that pulled in neighbouring Uganda and Rwanda.

The army last year launched a campaign against the ADF after the militia was blamed for dozens of massacres in the region, which also struggles inter-ethnic fighting.

The ADF is a mainly Muslim movement that originated in neighbouring Uganda in the 1990s, opposed to the rule of Ugandan President Yoweri Museveni.

In 1995, it moved into the DRC, which became its base of operations, although it has not carried out attacks inside Uganda for years.