Crimes against humanity were allegedly committed in eastern DRC last year when fighting erupted between the DRC military and the rebel March 23 Movement. Both parties to the conflict likely committed abuses, the United Nations said.
The International News Safety Institute said journalists in North Kivu province in eastern DRC should exercise "extreme caution" when working in the region, it said.
"At least 30 locals have been kidnapped in the area since April, with a majority abducted in the province's Rutshuru territory," INSI said in a statement.
At least one victim was released after the alleged kidnappers were paid a $5,000 ransom by unnamed donors.
ISNI said M23 rebels were suspected of playing a role in the kidnappings, though the movement denied the allegations.
Rebel leader Bosco Ntaganda surrendered to the International Criminal Court early this year to face war crimes charges.
The United Nations said "unidentified assailants" attacked the peacekeeping mission in DRC this week, killing a Pakistani member of the force.