RIGA, August 18 (RIA Novosti) - Latvia has asked Russia to provide more information on two Latvian nationals Moscow says were involved in the seizure of the merchant ship Arctic Sea, the Baltic state's Foreign Ministry said on Tuesday.

Russia's defense minister said earlier on Tuesday its frigate Ladny had freed the Arctic Sea cargo ship in the Atlantic without firing a single shot and eight suspected hijackers had been detained.

The Arctic Sea vessel was located 480 kms (300 miles) off Cape Verde on Monday after being missing in the Atlantic for over two weeks. In addition to the 15-person crew, there were eight unidentified people on board.

Anatoly Serdyukov said a speed boat carrying four Estonians, two Latvians and two Russians approached the Arctic Sea in the Swedish territorial waters on July 24.

Russia's Investigation Commission later said it had launched a criminal probe in connection with the hijacking.

The Maltese-flagged cargo ship left Finland with a cargo of timber on July 22 en route for Algeria. The ship last made radio contact with British coastguards on July 28. Finnish police confirmed that a $1.5 million ransom demand had been issued.

Last week, President Medvedev instructed the country's Navy to launch a search for the missing ship.