Russia attacks and seizes Ukraine ships

BBC:

Ukraine's navy says Russia has fired on and seized three of its vessels off the coast of the annexed Crimea, in a major escalation of tensions.

It said two gunboats and a tug were captured by Russian special forces after a chase. Two Ukrainian crew members were injured.

Russia is yet to comment on the claims.

The crisis began when Russia accused the Ukrainian ships of illegally entering its waters and stopped them from sailing into the Sea of Azov.

The Russians placed a cargo ship under a bridge in the Kerch Straight. It is the only access to the Sea of Azov, which is shared between the two countries.

Ukrainian President Petro Poroshenko later called an urgent meeting of his "war cabinet", his spokesperson said.
...

On Sunday morning, the Ukrainian ships tried to sail from the Black Sea port of Odessa to Mariupol in the Sea of Azov, Ukraine said.

It said Russia then tried to intercept the boats with one vessel ramming the Ukraine's Yana Kapa tug.

Russia later scrambled two fighter jets and two helicopters to monitor the Ukrainian vessels.

After placing the tanker under the bridge that spans the Kerch Strait, Russia said the traffic was suspended for security reasons.

Russian officials said Ukrainian naval reinforcements had been sent to the area and accused Kiev of trying "to create a conflict situation in this region"
...

Ukraine and Russia have a treaty declaring that both can use the sea of Azov.  Why the Russians chose to breach that treaty is unclear.