The Marshall Islands-flagged Liquid Velvet was seized on Monday in the Gulf of Aden en route to India. The 11,599 DWT vessel is owned by the Greek firm Elmira Tankers, according to the firm`s website.
"It was taken yesterday. It was going from Suez and heading to India," maritime editor Andrew Mwangura said.
Increasingly well-armed and violent Somali pirate gangs are expected to carry out more attacks as the monsoon season ends and the seas off the Horn of Africa flatten.
A pirate who gave his name as Khalif confirmed the attack. "We have hijacked the tanker and it is due to anchor near the shores of Garad," Khalif told Reuters by telephone from the pirate haven of Dhanane.
Piracy in the Gulf of Aden and the Indian Ocean costs the world economy billions of dollars a year. British Prime Minister David Cameron has said British merchant ships off the coast of Somalia will soon be allowed to carry armed guards.
Pirates operating from the Somali coast have raked in millions of dollars in ransoms from hijacked ships, including oil tankers. (*)