MOSCOW (AP) — Officials in Ukraine say they have seized a Russian tanker moored in the Black Sea.

The Ukrainian Security Service (SBU) said in a statement on Thursday that it seized the Russian tanker moored in a Ukrainian Black Sea port on Wednesday. Authorities said that the tanker was used in a Russian operation to block Ukrainian vessels from sailing through the Kerch Strait between the Black Sea and the Sea of Azov in November last year.

Russian ships fired on Ukrainian vessels in the Kerch Strait on Nov. 25 last year, sparking a major crisis amid already strained relations between the two countries. Russia seized the Ukrainian vessels and detained 24 Ukrainians onboard.