Ukraine seized a foreign cargo ship in the Black Sea off its Odesa region and detained the captain on suspicion of helping Moscow export Ukrainian grain from Russian-occupied Crimea, the Security Service of Ukraine (SBU) said Thursday.

The vessel, which it did not identify, was traveling under the flag of a central African country and repeatedly docked at the Crimean sea port of Sevastopol to pick up "looted" agricultural products in 2023-24, the SBU said.

Russian forces occupied swathes of Ukraine's southern agricultural regions in the first year of its invasion in 2022 and Kyiv has accused Russia of stealing and destroying its grain.

The SBU said the captain and 12 crew members helped Russia export Ukrainian grain taken from the occupied south to the Middle East for sale on behalf of Russia.

"The investigation is ongoing to establish all the circumstances of the crime and identify other persons involved in the illegal activity," the SBU said.

The captain, a citizen of a South Caucasus country, could face up to five years in prison for violating travel restrictions governing Ukraine's Russian-occupied territories, it said.

The Odesa region hub plays a key role in Ukraine's Black Sea exports that it has revived without Russia's assent after Moscow quit a UN-brokered deal last summer that had allowed Kyiv to export food during the war with Russia.

It was unclear when Ukraine last intercepted a ship although they have said Russia has been trading stolen Ukrainian grain since the 2022 invasion began.

Asked if there had been a change in Ukrainian policy, a source in law enforcement told Reuters, "This is our policy. This vessel and the captain worked for the occupiers and now he entered the waters controlled by Ukraine. And we had an immediate reaction."