Fr Jean-Paul Kakule was shot at several times with a machine gun on 25th February as he locked up the Mweso parish church.
Bishop Théophile Kaboy of Goma said the killing was "abominable, abhorrent and infernal".
No one has taken responsibility for the death, but the bishop suspects that the murder of 33-year-old Fr Kakule was a revenge killing, motivated by the Church's criticism of criminal groups.
"The real motives for the murder are still unclear, however the presence of the Church in Mweso presents serious interference with the action of criminal groups who sow terror," he said.
The bishop told Aid to the Church in Need 10 priests and five Sisters have been killed in the Democratic Republic of Congo since 1992.
"Criminal gangs can go about their evil business unhindered because there is no police presence," the bishop added.
In its 2014 Religious Freedom in the World report, Aid to the Church in Need noted 20 different militarised groups operating in the east of the country.
Bishop Kaboy appealed to national and international authorities to ensure justice and peace in the region: "While there have been notable advances in bringing peace to North Kivu, I see a general climate of concern about the successive assassinations and kidnappings for ransom."