Abuja, Nigeria — Police in Nigeria's oil rich Niger Delta say gunmen dressed in military uniforms killed three police escorts and abducted an oil executive.

Rivers State police spokesperson, Grace Iringe-Koko told VOA Friday that the police command has launched investigations into the killings and abduction to find the perpetrators.

She said the motive behind the attack is unclear and no group had claimed responsibility.

Iringe-Koko said the gunmen, disguised in military attire, ambushed two vehicles transporting the officers and a senior oil executive on Thursday around the Rumuokoro flyover bridge in Port Harcourt, the state capital.

They shot the officers and escaped with the oil executive in a vehicle.

Police said the abducted executive worked for the domestic oil and gas company IGPES Group, based in the area.

The company has yet to issue a statement on the incident.

"Investigation is ongoing, already the commissioner of police (CP) has deployed tactical teams to that end," Iringe-Koko told VOA via phone. "The state CID has been directed to carry out a discrete investigation on it."

Kidnapping for ransom is a major security challenge in Nigeria that authorities are struggling to address.

Rivers State is an oil-rich area in the Niger Delta region. It has seen activity by rebels who say they are protesting neglect and pollution of their environment by years of oil exploration.

Wealthy oil workers and businesspeople are often targeted by armed gangs there and across the nation.