Story highlights Oil tanker feared to have been target of first major pirate attack for years

The missing vessel has at least eight crew members on board

(CNN) An oil tanker has been hijacked off the coast of Somalia, raising fears Somali pirates could be back in action after almost five years.

The Aris 13, a Comoros-flagged oil tanker belonging to a Greek company, disappeared off the coast of the east African nation on Monday, according to a spokesman for the United Kingdom Maritime Trade Operations (UKMTO), based in Dubai.

The UKMTO spokesman confirmed to CNN that the ship's last known position was off the coast, near a town called Alula (Caluula).

"The vessel has been hijacked," he said. "It has been taken against its will to another location," he said.

But he said it was too early to say that the ship had been taken by pirates, and that there had so far been no request for a ransom.