Nigerian pirates have abducted another eight crew members on Wednesday, the second successful boarding in two days.
Security consultancy Dryad Global said a gang raided the 12,000-dwt general cargoship Stevia (built 1992), 28 nautical miles (52 km) off Brass.
The vessel was heading from Port Harcourt to Abidjan, Ivory Coast, at the time.
Security company Ambrey said prior to the incident, Stevia was underway at 7.6 knots with an estimated 5.6-metre freeboard.
The ship then started to drift, but resumed its course and speed more than three hours later.
Risk remains critical
Bulgarian operator Naviborn could not be contacted.
This is the 27th kidnapping in the Gulf of Guinea this year, bringing the total number of seafarers seized to 138.
The risk in the area has remained at critical after a spike in attacks since October, when the monsoon season ended.
The boarding was the ninth pirate incident so far this month.
Dryad advised ships to maintain the highest levels of vigilance in the region.
Piracy reporting body IMB recommends vessels stay at least 200 to 250 nautical miles offshore where possible.
On Tuesday, gunmen boarded the 711-dwt general cargoship Cap Saint Georges (built 1973) 28 nautical miles (52 km) south-east of Bonga, seizing five crew members.
The abducted seafarers were reported as three Cameroonians, a Ghanaian national and one Sierra Leonean.
The two kidnappings earlier in the week have involved smaller, more vulnerable vessels nearer to shore, after a series of largely unsuccessful boardings of tankers further out to sea.
