A Nigerian court on Friday jailed 14 foreign sailors from Russia, Ukraine, Philippine and Japan between two and five years for unlawful dealing in petroleum products in the country.

The federal high court in Lagos found the suspects guilty of illegally transporting 1,738 tonnes of crude oil and some 4,500 tonnes of petrol, also called gasoline, in their vessel MT Anukpet Emerald.

Judge Ibrahim Buba sentenced 11 of the 14 foreigners to two years’ jail or alternatively pay a fine of two million naira (10,000 dollars) each.

The remaining three — all Russians — were given five years each in absentia without an option of fine for jumping bail.

The court also ordered that the vessel and the seized petroleum products be forfeited to the Nigerian government.

The Nigerian navy arrested the sailors and the vessel in February 2015 and handed the case to the Economic and Financial Crimes Commission (EFCC) for prosecution.

It was not immediately clear if the products onboard the vessel were to be taken out of Nigeria and if so, to which country they were headed.

Nigeria, Africa’s biggest oil producer loses billions of dollars each year from the theft of crude from sabotaged pipelines and illegal refining of oil products.

The oil is sold on the black market, depriving the continent’s most populous state of an estimated $6 billion a year in lost revenue.

Convictions for oil smuggling are common but in most cases the offenders get away with a fine.