Six Turkish sailors kidnapped early this month from aboard their vessel off the coast of Nigeria have been released unhurt, a maritime consultancy firm said on Tuesday.
Pirates attacked the merchant tanker used for crude oil operations on April 11 while it was steaming through the oil-rich Niger Delta and seized the sailors, including the captain.
Dirk Steffen, director of maritime security at the Denmark-based Risk Intelligence firm, told AFP the abducted men had been freed and that they were in "good health".
He did not say whether ransom had been paid before the sailors were released in a region increasingly hit by piracy.
Turkey's Deniz News Agency said the ship, the M/T Puli, was owned by Kaptanoglu Shipping and was en route from Port Gentil in Gabon to the Ivory Coast capital, Abidjan, when it was attacked.
The Nigerian navy could not immediately confirm the release of the sailors.
Ship hijackings have become more frequent since President Muhammadu Buhari took office in Nigeria last year and started winding down an amnesty to former militants in the delta region.
Payments were offered in exchange for an end to violence, which included kidnappings of oil workers and sabotage of pipelines that plagued the region in the 2000s.
Steffen said some 40 vessels have been attacked since the beginning of the year alone in the region.
"According to our research 40 vessels have been attacked in Nigerian waters, inside and outside territorial waters, since 1 January 2016," he said.
"Fifteen of those attacks involved kidnappings. Forty-four Nigerians and 30 foreigners have been kidnapped from boats and ships working in, and transiting through, Nigerian waters in 2016," he said.