Owners have been warned to be vigilant after Somali pirates attacked a merchant vessel for the first time in two and a half years.

European naval force EUNavfor confirmed the 52,000-dwt Offen Tankers chemical carrier CPO Korea (built 2009) was approached off the country’s coast on 22 October.

Operation commander Major General Rob Magowan said the vessel was attacked by six armed men 330 miles from land.

“During the attack a number of shots were exchanged between the six armed men, who were in a fast-moving skiff, and the armed security team on board CPO Korea,” he added.

“The suspected pirates eventually broke away after CPO Korea’s crew successfully implemented self-protection measures by increasing speed, altering course and rigging fire hoses to thwart the attack.”

CPO Korea was able to continue its transit in the Indian Ocean, with no casualties reported.

Pirate attacks in the Gulf of Aden and Indian Ocean surged in 2008 and by January 2011 over 700 hostages and 30 vessels were being held by Somali pirates, EUNavfor said.

But since then, naval patrols and the presence of security guards have reduced the threat.

Magowan said: “This attack shows that pirates still have the intent to attack ships for ransom and cause misery to seafarers and their families.

“It is imperative that the international community remains vigilant.”

Offen Tankers said: “Despite the decreasing number of attacks in the region the imminent risk of Somalian piracy still exists and needs to be addressed accordingly by owners and charterers alike.”