Gunmen ambushed and killed at least 16 Christians following a New Year's Day service in southern Nigeria early Monday, according to authorities.
The attack happened in the town of Omuku, about 50 miles from the state capital Port Harcourt, an oil-rich region of Rivers state, BBC News reported.
In a coordinated effort, the unidentified attackers fired on worshippers in two different locations of the church as they were leaving the service at about 12:20 a.m.
First responders transported at least 12 others to the hospital, the Christian Post reported.
New Year's celebratory fireworks made it difficult for nearby residents to recognize the sound of the gunshots fired at the church.
What are officials saying?
"The Commissioner of Police has launched a manhunt for the bandits to ensure they are arrested and prosecuted," public relations official Nnamdi Omon said, according to the Post.
Violent crimes between rival gangs in the region have increased over the past year since the government allowed an amnesty program for former gang members to lapse, UPI reported. The program had helped to bring some peace to the region where militants are trying to gain control of the country's oil wealth.
It's not immediately clear if the attack is related to the oil conflict.
The Post also reported that hundreds of Christians died in attacks in 2017 including four who were killed two days before Christmas while they were caroling. The suspects were identified as Fulani herdsmen who are believed to have murdered hundreds of Christians over the last year.