The Arctic Sea disappeared in a busy European shipping lane last July
A Moscow court has handed down a five-year jail term to one of the eight men detained over the mysterious seizure of the cargo ship Arctic Sea.
Andrei Lunev, from the Estonian capital Tallinn, is the first to be sentenced over the incident last July. He was found guilty of piracy.
The Maltese-flagged Arctic Sea and its 15 Russian crew vanished soon after leaving Finland with a cargo of timber.
The mystery sparked speculation about a possible arms shipment for Iran.
Russia dismissed speculation that Russian S-300 missiles were on board the ship.
The Arctic Sea was eventually found on 16 August off West Africa. Moscow announced that the Russian navy had captured the hijackers and rescued the crew.
Eight were charged over the incident - citizens of Russia, Estonia and Latvia.
This week Lunev and one of the others - Dmitry Savins - admitted their guilt, Russia's RIA Novosti news agency said.
Lunev could have faced much longer but had agreed to plead guilty as part of a deal with prosecutors.
While the authorities will be pleased to see these men convicted, there are still many unanswered questions about the whole Arctic Sea affair, which became one of the great mysteries of last summer, the BBC's Richard Galpin in Moscow says.
He adds that a lawyer representing one of the accused told the BBC last September that his client said they had been set up: that they had not hijacked the ship, instead they had been rescued by it.
The journalist who first broke the story that the ship had gone missing fled Russia shortly afterwards, saying he had been warned to leave after suggesting it may have been carrying a secret consignment of weapons.
The crew and their families have also been under intense pressure to keep quiet, our correspondent says.
Also last September, a senior figure close to Israeli intelligence told the BBC that Israel had been linked to the interception of the Arctic Sea.
The source said Israel had told Moscow it knew the ship was secretly carrying a Russian air defence system for Iran. There has been no official confirmation of the report.