Somali pirates have hijacked a Saudi tanker with 14 crew onboard, a spokesman for the European Union Naval Force said Wednesday.

The Al Nisr Al Saudi usually carried fuel oil but was empty when it was taken in the Gulf of Aden on Monday, said Cmdr. John Harbour. The captain of the ship is Greek and the nationalities of the rest of the crew were not known, but they are believed to be safe.

The 5,136 ton ship was not registered with maritime authorities and was outside the designated route patrolled by naval warships, Harbour said.

Although the number of pirate attacks increased in 2009, the number of ships successfully hijacked remained about the same as in 2008 because of the naval patrols in the Gulf of Aden and better training for sailors, maritime officials say.

Somali pirates are currently holding six hijacked ships and 132 sailors, including those aboard the Al Nisr Al Saudi, according to the EU Naval Force.

That figure may increase in coming months. Pirate attacks typically spike during March, April and May, when calmer seas make it easier for pirates to board ships.

Somalia has been torn apart by civil war for the past 19 years. The shaky U.N.-backed government is barely able to hold a few blocks of its capital and is too focused on fighting an Islamist insurgency to send its forces after pirates.