A Russian warship has seized three pirate boats as they reportedly closed in on an Iranian trawler off the coast of Somalia, a navy spokesman has said.

Ten pirates are being held by Russian naval officers after the nuclear-powered cruiser Peter the Great seized the vessels, Igor Dygalo told the AFP news agency.

Grenade launchers, automatic rifles and landmines were discovered on board the boats.

He said the pirates had been spotted from the cruiser's helicopter, south-east of the Yemeni island of Socotra in the Indian Ocean.

"It was visually established how weapons were being dumped from the boats into the sea," he said.

The capture came after the crew of a Ukrainian ship hijacked by Somali pirates arrived home, after a 19-week ordeal.

The crew, which included 17 Ukrainians, two Russians and one Latvian, were met at Kiev's Borispol airport by their families and Viktor Yushchenko, the country's president.

The MV Faina, which was carrying battle tanks and other arms, docked at the port of Mombasa on Thursday.

Ransom paid

The ship was released by pirates last week, after a ransom of $3.2 million was paid to the Somali hijackers, regional maritime sources and members of the gang said.

The vessel's capture was one of the longest and most prominent hijackings since Somali piracy surged in 2007.

The Faina's captain died, reportedly of natural causes, two days after it was seized.

Pirates from Somalia are known to target merchant ships sailing through the Gulf of Aden.

Navies from the US, Britain, India and Russia now patrol the sea off the Horn of Africa in an attempt to prevent hijackings.