A group of Somali pirates are apprehended by several Portuguese marines. (Photo Courtesy NATO)

Somali pirates have reportedly seized a Greek-owned oil tanker and its 28 crewmembers more than 1000 kilometers off the coast of Somalia.

The supertanker, Maran Centaurus, which can transport more than 2-million barrels of oil, was sailing from Jeddah in Saudi Arabia to the New Orleans in United States, when pirates seized it on Sunday, Greek officials reported on Monday.

According to European Union Naval force, the ship weighs some 300,000 tonnes and is believed to be one of the largest yet seized by Somali pirates.

The Maran Tankers Management, which operates the vessel, confirmed the seizure, saying the crew consisting of 16 Filipinos, nine Greeks, two Ukrainians and one Romanian are well.

Last year on November 2008, Somalia-based sea gangs seized a Saudi-owned supertanker the Sirius Star weighing 318,000 and carrying two million barrels of oil - It weighs tonnes.

The tanker was released in January after a ransom of $3m was paid. Currently, more than a dozen ships and nearly 300 crew are held by pirates for ransom.