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Russia and Ukraine are at a dangerous standoff threatening to escalate into conflict in the wake of Russia's seizure of three Ukrainian naval vessels and all 24 crew members onboard in the Azov Sea.
Russia's government said the seizure and subsequent imprisonment of all crew members is a result of Ukrainian "provocation."
Ukraine: Martial law and entry ban
In response, Ukraine's government implemented a month-long martial law in border areas and is banning Russian men aged 16 to 60 from entering Ukraine.
"Special forces of the Russian Federation attacked Ukrainian military ships in the Sea of Azov and Kersch Strait and we recognize it as an act of aggression, as an act of war," said Yuriy Husyev, former Ukraine Deputy Defense Minister.
Russia-backed forces in Crimea in 2014. /CGTN Photo
Russia-backed forces in Crimea in 2014. /CGTN Photo
What happened and NATO appeal
The naval incident happened off the coast of Crimea at the Kerch Strait entrance to the Black Sea. Russian naval vessels rammed and then seized the Ukraine ships and crew members.
The incident is the most acute escalation between the sides since Russia occupied and annexed Crimea from Ukraine in 2014 - the area where the incident occurred. Ukrainians are concerned Russia will eventually make moves to occupy more parts, or eventually all of Ukraine.
An early 2000's treaty between the two countries stipulates access to the Kerch Strait and Sea of Azov. Russia claims the incident occurred in Russian territorial waters.
Fearing Russian invasion, Ukraine leaders are asking NATO to deploy vessels to the Black Sea and Azov Sea areas. Ukraine is not a NATO member but does have NATO support.
However, it is unlikely NATO will send naval support anytime soon.
Myroslov Hai poses with his uniform. /CGTN Photo
Myroslov Hai poses with his uniform. /CGTN Photo
Reservists on standby
As Ukraine's military holds nationwide drills on Monday, reserve members are readying for a potential call-up.
Myroslov Hai, a special forces veteran and father of two children, fought against Russia in Eastern Ukraine in 2015 and says he is mentally and physically preparing to return to the front.
"I've learned Russia's laws and history, and I understand it's just a matter of time before they try and take Ukraine," Hai said. "If I don't fight now, my children may end up living under occupation - or immigration."