Russia has seized three Ukrainian naval vessels off the coast of the Crimean Peninsula, further escalating tensions between the two countries.
It all reportedly started when two Ukrainian gunboats and a tugboat tried to pass through the Kerch Strait. For perspective, the Strait is an important shipping route for several Ukrainian port cities, but it runs by Crimea, which Russia annexed in 2014.
When the three Ukrainian naval vessels tried crossing through the Strait under a bridge on Sunday, they found the path blocked by a Russian tanker. Ukraine says Russians tried to intercept the vessels and rammed the tugboat. Several Ukrainian crew members were reportedly injured at some point during the fray.
Russia says the Ukrainian vessels were in its waters illegally, but Ukraine says it has a right to use the Strait and told Russia it planned to pass through.
Things have been tense between Ukraine and Russia for a while now. And Russia has begun inspecting all ships going to and from Ukrainian ports, even though a 15-year-old treaty between the two countries says the Kerch Strait and Sea of Azov are shared waters.
On Monday, Ukrainian President Petro Poroshenko signed a decree to implement martial law. It could restrict some civil liberties and increase the state's power, possibly allowing Poroshenko to postpone Ukraine's presidential election set for March, which he's reportedly unlikely to win. Parliament still has to approve the martial law measure for it to take effect.
And Russia called for an emergency U.N. Security Council meeting on Monday. The U.N. Russian Mission confirmed that the meeting would address the "maintenance of international peace and security" regarding the Russia-Ukraine water border crisis.
A NATO spokeswoman said the organization is monitoring the developments in the Sea of Azov and the Kerch Strait and called for de-escalation. She also said: "NATO fully supports Ukraine's sovereignty and its territorial integrity, including its navigational rights in its territorial waters."
Additional reporting from Newsy affiliate CNN.