https://news.sky.com/story/russia-fires-at-ukraine-ships-in-black-sea-11563775

Russia has opened fire on Ukrainian ships and captured three vessels in a major escalation of tensions off the coast of Crimea.

Three sailors have been wounded after the Ukrainian navy said two artillery boats were hit by the strikes in the Black Sea.

Russia's Federal Security Service (FSB) said it used weapons after the Ukrainian ships ignored demands to stop and that it impounded three vessels which had illegally crossed the border.

Ukraine attempted to invade the Kerch Strait.

https://amp.theguardian.com/world/2018/nov/26/nato-calls-for-calm-after-boats-seized-in-russia-ukraine-clashes-kerch-strait

The Russian ambassador, Dmitry Polyanskiy, claimed the Ukrainian ships had entered Russian territorial waters and portrayed the incident as a long-planned provocation by the Ukrainian president, Petro Poroshenko, and his western backers to distract from Poroshenko’s unpopularity in the run-up to elections scheduled for next March. Ukraine’s declaration of martial law “is about cancelling the elections”, he said.

Polyanskiy said the Ukrainian ships had “illegally crossed Russia’s border” and the “responsibility lies with those who gave the illegal order” for the ships to cross the Kerch strait.