Ukraine has accused Russia of ramming one of its boats off the coast of the annexed Crimea, amid rising tensions.
The "openly aggressive actions" occurred as three of its vessels sailed from the Black Sea port of Odessa to Mariupol in the Sea of Azov, Kiev said.
Ukraine's Yana Kapu tug suffered damage to its engine, guard rail and outer shell, the Ukrainian navy said.
But Russia said the ships were in its waters, and accused the Ukrainians of "provocative actions".
Russia has now blocked access to the Sea of Azov with a tanker under the bridge that spans the Kerch Strait.
Tensions have risen in the seas off the Crimean peninsula - annexed by Russia in 2014 - in recent months.

[link to www.bbc.com (secure)]