West African pirates boarded a tanker managed by Evangelos Marinakis-controlled Capital Ship Management on Sunday night, kidnapping four crew members.
Security consultancy Dryad Global said the 38,000-dwt Agisilaos (built 2006) was attacked by an unknown number of gunmen while underway in Ghanaian waters, 75 nautical miles (139 km) south of Lome in Togo.
The vessel is understood to have a crew of 22 personnel, including Russian, Romanian and Filipino nationals.
This is the 24th confirmed kidnapping incident in the waters of the Gulf of Guinea this year, with 122 crew kidnapped from vessels.
AIS data showed the ship anchored in Lome on Monday morning.
The incident occurred 5 nautical miles from the western edge of the Gulf of Guinea high risk area.
According to AIS, the vessel changed direction to starboard and dramatically reduced speed, conducting evasive manoeuvres to avoid boarding.
Cash and equipment stolen
Security consultancy Ambrey said the tanker was laden when six armed criminals boarded.
The gang also stole $16,000 in cash and electronic equipment.
"Prior to the attack, the vessel was underway at 12.7 knots from Pointe-Noire, Republic of the Congo, to Lome," Ambrey said.
Evasive manoeuvres included an increase of speed out of a starboard turn. The tanker then slowed to 3.7 knots and later resumed its course.
The vessel had an estimated 7.4-metre freeboard.
Capital Ship Management confirmed the incident and the abduction.
"All other crew members are safe and well and the vessel is now safely at anchorage in Lome, Togo," the company added.
"Capital has activated its emergency response team, and is working closely with all relevant authorities to resolve the situation as quickly as possible. Our top priority at this moment in time is the safe and timely return of our crew to their loved ones."
US company Diamond S Shipping, which owns the vessel through its merger with the tanker business of Marinakis' Capital Product Partners, confirmed there were 22 seafarers on board.
"There have been no reports of injuries at this time. All appropriate authorities have been notified and Diamond S is fully supporting Capital as they respond to this situation," the company added.
Ambrey also reported a fishing vessel suffered an attack while underway 6.9 nautical miles from Cameroon on Monday.
Pirates in a speedboat fired on the ship, wounding one Cameroonian Bataillon d'Intervention Rapide (BIR) officer.
The BIR team returned fire and the criminals escaped, although several were injured.
'Desperation' of gangs
"While the design of this vessel does not signal any overarching vulnerabilities, this incident highlights the desperation of perpetrators in the region," Dryad said.
"Counter-piracy operations and logistical strains mean larger vessels may be targeted should attacks targeting smaller vessels with vulnerable characteristics be unsuccessful."
Dryad rates the possibility of further attacks on vessels underway as highly likely. The risk is described as critical.
On Wednesday, 10 crew members from a St Kitts-flagged general cargoship boarded off Nigeria were kidnapped.
The 2,500-dwt Milan (built 1982) came under attack on Wednesday evening, 14 nautical miles north-west of Chevron's Pennington Terminal and 10 nautical miles from shore.
The vessel was in transit from Escravos in Nigeria to Douala, Cameroon.
This followed two other kidnappings in the previous week, one of which happened 22 nautical miles from Sunday's raid. But there have also been a series of unsuccessful attacks on tankers in the region as well.
