A Tanzanian-flagged oil tanker was hijacked by suspected Somali pirates off the coast of Yemen and later taken to waters near Somalia's northeastern Bari region, security sources and local officials said on Sunday.

The vessel, identified as the MT ASANA, was reportedly seized on Friday after leaving the Yemeni port city of Mukalla.

Officials said the tanker is now being held off the coast of Caluula in Puntland's Bari region.

According to security sources, seven armed Somali pirates were involved in the hijacking. They spoke on condition of anonymity because they were not authorised to discuss the incident publicly.

Vessel-tracking data reviewed by The Associated Press showed the tanker moving slowly through the Gulf of Aden on Friday while transmitting Bosaso, Somalia, as its destination. The ship was travelling at about two knots, an unusually slow speed that matches earlier reports indicating it had sent a distress signal during the incident.

It was not immediately known how many crew members were on board or whether anyone was injured. The nationalities of the crew have also not been disclosed.

Authorities in Puntland have not yet commented publicly on the reported hijacking. There has also been no immediate statement from the vessel's owner or operator, while international naval forces patrolling the region have yet to issue an update.

The incident is the latest in a growing number of attacks blamed on Somali pirates, whose activities have resurfaced in the Gulf of Aden and the western Indian Ocean after years of relative calm.

Maritime security experts say the recent increase in piracy has been linked to ongoing security challenges at sea and a reduction in international naval patrols in the region.