Nigeria moves Russian arms smuggling suspects to police cells

* Russian sailors arrested in Nigerian waters in October

* Nigerian authorities say seized thousands of munitions

ABUJA Jan 9 (Reuters) - Fifteen Russian sailors detained by Nigeria's navy in October on suspicion of arms smuggling have been transferred to police cells for prosecution, a naval spokesman said on Wednesday.

Nigerian authorities intercepted a ship and arrested its all-Russian crew on Oct. 23 after they found several guns and about 8,500 rounds of ammunition aboard.

"On Monday, we handed over the crew to the police as we have completed preliminary investigations. The ship and the weapons are still in our custody," Lieutenant Commander Jerry Omodara, spokesman for the Western Naval Command, said by telephone.

Russian authorities were not immediately available for comment, nor were officials from the Moran Security Group, the Russian company that owns the vessel.

Omodara said the boat was initially stopped because it was in Nigerian waters without permission.

Arms smuggling is rife to and through Nigeria. Africa's top oil producer faces multiple security challenges, including Islamist rebels in the north, armed robbery or kidnapping gangs in the south, and oil thieves and pirates in the southeast.

The country is also sometimes used as a conduit for shipping arms into other conflict-ridden parts of West Africa.

In 2010, a consignment of rocket launchers, grenades and other explosives from Iran was seized in Lagos, causing a diplomatic incident between Nigerian and Iran, and later between Iran and Senegal, which accused Iranian security forces of trying to supply weapons to its Casamance rebels. (Reporting by Isaac Abrak; Writing by Tim Cocks; Editing by Mark Heinrich)