One witness, Khaled Burqan, told Jordan's al-Mamlaka state television that the two assailants, armed with a rifle and a pistol, fired at the congregation for several minutes. Between 150 and 200 people were inside the church at the time of the funeral.
The gunmen arrived by car and fled immediately after the attack, according to the Public Security Directorate. Government spokesman Mohammad al-Momani condemned the assault as 'heinous' and confirmed that security forces had been deployed to the area. Authorities said an investigation is under way and that further details would be released as they become available.
The state-run news agency earlier reported a death toll of seven before officials confirmed the lower count of six dead and 28 injured.
No group has yet claimed responsibility for the attack. Violence against civilians is rare in Jordan, noted for its stability in the Middle East. The Karak governorate has a significant Christian community within the majority-Muslim kingdom. The targeting of a religious ceremony has drawn widespread condemnation and raised concerns for the safety of minority groups in the region.