Pirates who hijacked the China-bound, Russian-owned MV Moscow University tanker 565 km off the coast of Yemen warned against any rescue attempt, saying this would endanger the Russian crew.
"A Russian warship is moving towards the tanker," Russian defense ministry spokesman Alexei Kuznetsov said. The Chief of the Russian General Staff cut short a visit to NATO headquarters in Brussels to coordinate the military's response, he added.
The vessel had been traveling under a Liberian flag from Sudan to the Chinese port of Nigbo with 86,000 tonnes of oil owned by Chinese refiner Unipec, a Russian shipping source said. Maritime experts said the tanker had a deadweight of 106,474 tons.
"The crew members locked themselves in the radar room. This ship has been hijacked," Commander Rear Adm. Jan Thornqvist of the European Union's Navfor naval force told reporters in the Kenyan port of Mombasa.
Somali sea bandits continue to outwit an international fleet of warships in the busy shipping lane linking Europe with Asia, raking in tens of millions of dollars in ransoms.
One pirate who identified himself as Abdi said the tanker was heading to a pirate haven on the coast of central Somalia.
Russia's permanent representative to NATO, Dmitry Rogozin, said the warship would not attack the tanker as the safety of the crew was the top priority, Interfax news agency reported.
The ship will reach the tanker at around 2100 GMT, he said.
Some oil tankers are sailing around southern Africa and further east into the Indian Ocean away from Somalia's coastline to avoid the Gulf of Aden and pirates who are striking deeper out at sea, shipping experts say.
But many are running the gauntlet through the busy Gulf of Aden shipping lane, where warships operate convoys and have set up transit corridors. The tanker had not registered with the Maritime Security Centre Horn of Africa, EU NAVFOR said.
The use of mother ships has enabled Somali pirates to strike as far as the Mozambique Channel and off India's coast in recent months, launching smaller boats known as skiffs against ships.
About 7 percent of world oil consumption passes through the Gulf of Aden.
