A UK tanker has reported having to take evasive measures after an approach by what appeared to be a fishing vessel way out in the Gulf of Guinea.

The incident involving Norbulk Shipping's 13,100-dwt Marshall Islands-flagged chemical carrier Valley Oak (built 2008) took place 198 nautical miles (367km) south of Cotonou in Benin on Wednesday evening, piracy reporting bodies said.

Security consultancy Dryad Global said the ship reported being approached by a "fishing" vessel with proper navigation lights at an estimated speed of 16.5 knots.

This ship attempted to close with the tanker, which conducted evasive manoeuvres before the other craft aborted its approach.

Both the tanker and its crew were reported safe.

Attacks continuing

Norbulk has been contacted for further information.

This is the seventh reported incident involving a pirate attack on a tanker in the Gulf of Guinea in the last week.

Five of these took place off Benin.

"Incidents remain focused on the waters south of Cotonou with a second area in the waters [off] south-west Bayelsa state, Nigeria," Dryad said.

"Despite the prevalence of attacks within these areas, the threat remains fluid and attack locations are liable to alter depending upon traffic density."

Shipowners' organisation Danish Shipping told TradeWinds on Thursday it was very concerned by the situation off West Africa, with attacks likely to continue after the monsoon season ended.

No crew members have been kidnapped in these latest incidents, due to evasive action or seafarers retreating to citadels.