Forces on the Marshal Shaposhnikov freed the captured tanker
Russian forces have freed the crew of a Russian oil tanker seized by Somali pirates off the coast of Yemen, in a dramatic rescue operation.
Forces based on the warship Marshal Shaposhnikov approached the tanker with 23 Russian crew on board.
The Russian forces then boarded the Moscow University tanker, freeing the crew who had locked themselves in a safe room after disabling their ship.
As they did so, the pirates opened fire, sparking a shoot-out.
Before boarding the tanker, the Russian forces carried out reconnaissance from a helicopter, RIA-Novosti reports.
Ten pirates have been arrested, and one was killed during the gun battle. They are being held aboard the tanker, Russian defence ministry spokesman Col Alexei Kuznetsov said.
They will be transferred to Moscow to face charges.
"Pirates have released the tanker... All crew on board the tanker are alive and well," a spokeswoman for the Russian shipping company that owns the tanker, Novoship, told Reuters news agency.
Novoship praised the operation as one carried out "in the best traditions of the Russian naval mariners".
The decision to free the ship was made knowing "that the crew was under safe cover inaccessible to the pirates", Novoship added.
BBC News, Moscow
Navy officials involved in the international operation to protect commercial shipping off the Horn of Africa say there has been a huge increase in the number of attacks by pirates so far this year - and this despite the presence of up to 40 warships in the area from the European Union, Nato, Russia and India.
So now the foreign navies are becoming more aggressive. According to Cdr John Harbour, the main spokesman for the EU Navy Force, one new tactic is to lie in wait near the pirates' main bases and take them out when they set sail on a hijacking mission.
Also this year, there have been three incidents when foreign forces have managed to board hijacked boats and capture the pirates. But this can only be done if all the crew have managed to lock themselves in a secure room on board the ship and have contacted the nearest navy forces to say they are safe - exactly what happened in Thursday's incident.
Although there are dozens of warships patrolling the Indian Ocean and the Gulf of Aden, it is rare for rescue efforts to be launched once pirates have boarded a vessel as it is often felt that intervening would endanger the hostages, says the BBC's Will Ross in Nairobi.
But in this case, the crew switched off the engine and locked themselves in a strong room with a reinforced door.
It also helped that the warship was less than a day away, says the BBC's Richard Galpin in Moscow.
So while the idea of having a secure room in all commercial ships sailing the route near Somalia is a good one, it can only work in very specific circumstances, he says.
The Moscow University was seized on Wednesday in the Gulf of Aden, off the coast of Yemen, as it sailed for China, carrying more than 80,000 tonnes of crude oil worth some $50m (£33m).
The Gulf of Aden is one of the world busiest shipping routes, and the Russians, Europeans and Americans have all deployed navy forces in the region after a growing number of attacks by pirates on commercial vessels, our correspondent adds.
Even so, pirates are reported to be holding more than 20 foreign ships with almost 400 sailors.
The Marshal Shaposhnikov was sent on Wednesday to rescue the hijacked tanker.