MOSCOW — In a move likely to further ratchet up tensions between Moscow and Kiev, Ukraine seized a Russian tanker that it said was used during a naval confrontation last year to block passage through a disputed waterway linked to the Black Sea, Ukraine’s security service said on Thursday.

During the clash over the waterway, the Kerch Strait, Russia seized three small Ukrainian naval vessels. Eight months later, it still holds their crews prisoner, a sore point in relations between the countries.

The tanker taken by Ukraine was impounded after entering the port of Izmail in the Odessa region, the security agency, known as the S.B.U., announced in a statement on its Facebook page.

The Russian-flagged ship, now called the Nika Spirit, used to carry the name Neyma, the statement said. Under that name, the tanker blockaded the navigation route under the Kerch Bridge in November by anchoring across the channel, the statement said.