Security Officer stand guard in Janjala Village, Nigeria.

Gunmen have kidnapped two Turkish nationals from their hotel in southern Nigeria’s oil-rich Akwa Ibom state, police said Tuesday in the latest unrest to hit the restive Niger Delta.

“Two Turkish nationals working for a construction company in Onna local government area were abducted from their hotel rooms on Sunday,” state police spokesman Chukwu Okechukwu told AFP.

He said the men, who work for BKS Construction Co. which is based in Onna, were seized by gunmen from a hotel in Eket, an industrial city which is home to Mobil, the Nigerian subsidiary of US oil giant Exxon. He said efforts were under way to free the pair.

It was not immediately clear why they were kidnapped and so far no group has claimed responsibility.

In January, a Turkish teacher was abducted from a school just outside Lagos along with another two staff members and five students, police said, indicating that they were freed two weeks later.

No group claimed responsibility.

Kidnapping for ransom was rife in the Niger Delta until a 2009 government amnesty drastically reduced unrest in the region.

Most kidnap victims were released unhurt after ransom payments.

But the region has seen a resurgence of militancy since 2016, cutting Nigeria’s oil output at a time of global low crude prices, hurting government revenue and forcing Africa’s most populous country into a recession.

An ongoing government truce with the rebels has significantly ramped up the nation’s oil production.