Michael Sharp, a US citizen, and Zaida Catalan, of Swedish nationality, had "fallen into the hands of negative forces not yet identified", along with four Congolese they were with, the government said in a statement.
A man with Hesston ties has been kidnapped in the Congo, where he has spent the past several years working for the peaceful resolution of conflict.
An American was abducted while working as a United Nations official in central Africa, his father told NBC News on Tuesday.
Sharp is the son of Hesston College professor John Sharp and medical worker Michele Miller Sharp.
"We're hopeful", John Sharp said.
The government released the identities of the foreign United Nations workers: American Michael Sharp and Swede Zaida Catalan. There was no information on who the kidnappers may have been, Congo government spokesman Lambert Mende said.More news: Tom Brady's Jersey is Found...in Mexico
The Congolese government did not say when the kidnapping took place.
Congo is home to multiple militias competing for stakes this vast Central African nation's rich mineral resources.
Sharp is a 2001 graduate of Bethany Christian Schools in Goshen, Indiana, and a 2005 graduate of Eastern Mennonite University, Harrisonburg, Virginia.
Reports by Reuters, Al Jazeera and other outlets note that the Kasai region has seen fighting and rebellion since September 2016 after the August killing by government forces of Kamwina Nsapu. Prior to that, Sharp worked with the Mennonite Central Committee as the Eastern Congo Coordinator.
The Associated Press reports the U.S. Embassy in Kinshasa is aware of reports about Sharp, and the State Department is monitoring the situation. "Apparently, he had some success in persuading some to give up child soldiers".