Russian special forces stormed a hijacked oil tanker yesterday freeing the crew, killing one pirate and arresting another 10.
The raid on the Liberian-flagged ship Moscow University came 24 hours after the pirates had taken the ship and the crew of 23 locked itself in a safe room.
The vessel is carrying 86,000 tons of crude oil worth about $50 million.
The special forces had been aboard the Russian anti-submarine destroyer Marshal Shaposhnikov, which rushed to the scene off the coast of Yemen after Wednesday's hijacking.
A helicopter was sent to investigate and was fired on by the pirates, EU Naval Force said. The Russian warship returned fire.
Special forces troops on the helicopter abseiled down to the Moscow University.
Russia plans to send the pirates to Moscow to face a criminal trial.
The crew of the Moscow University had switched off the engines before locking themselves in the safe room, leaving the ship drifting.
Safe rooms are stocked with food, water and communications equipment and have reinforced doors that can only be opened from the inside.
The ship's owner, Novoship, said the decision to storm it was made knowing "that the crew was under safe cover inaccessible to the pirates and that the lives and health of the sailors was not threatened by anything".
A spokesman for the EU Naval Force called the rescue "an excellent operation all around". He said the EU Naval Force had been working at a tactical level with the Russians.
The attack was about 500 miles east of the Somali coast as the Moscow University sailed from the Red Sea to China, the ship's owner said. Novoship is a subsidiary of Sovcomflot, which is owned by the Russian government.
The military intervention follows a trend. International forces have been more aggressively combating piracy. EU Naval Force ships are disrupting pirate groups and destroying their ships at a much higher rate than in previous years. US warships have fired back on pirates and destroyed their boats in several skirmishes in the last several weeks.
In February, Danish special forces prevented the hijacking of a ship after pirates had boarded it.
But pirates are still holding more than 300 hostages taken from ships off East Africa in the last several months.