The preachers were taken over the weekend from the Kiseguro area, in the restive province of North Kivu, province Governor Julien Paluku told AFP.
"We have referred the case to our foreign affairs mission so that it can alert its Tanzanian counterparts," he added.
Kidnappings for ransom, often with physical violence against the hostages, are frequent in the territory around Kiseguro.
Several armed groups, including the ethnic Hutu militia Democratic Forces for the Liberation of Rwanda (FDLR), operate in the east of DR Congo, which is a Christian-majority country.
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Just a few months ago a Muslim leader in the area was taken hostage and later released in exchange for a ransom, he added.
It is not clear who captured the preachers, but authorities speculated that FDLR or local youths could be behind the kidnapping.
The FDLR has been active in Democratic Republic of Congo -- which borders both Rwanda and Burundi -- since crossing over from Rwanda after the 1994 genocide of mainly Tutsi people there.