Ukrainian President Petro Poroshenko on Sunday called for a 60-day period of martial law, which would curtail public demonstrations, suspend elections and potentially implement required military service.

The decree comes amid escalating tensions with Russia. This past weekend the Ukrainian Navy reported that sailors from three of its ships had been arrested by Russian forces in the Sea of Azov.

Initial numbers, according to Poroshenko, indicate that six Ukrainians were injured in the raid.

I want to emphasize separately that we have all irrefutable evidence that this aggression, this attack on the Ukrainian Navy’s warships was not a mistake, not an accident, but a deliberate action. Including the use of weapons against Ukrainian sailors. The use of weapons had severe consequences, six sailors, according to the preliminary information, were wounded[].

Poroshenko stated that martial law was not for offensive military action and only to protect Ukrainian borders. In response to the incident, Russia closed the Kerch Strait, which connects the Black Sea and the Sea of Azov, to all non-military ships. The Kerch Strait separates mainland Russia from the recently annexed Crimea.

The Verkhovna Rada, Ukraine’s unicameral parliament, must ratify the martial law measure. A special session to address the issue will be held later Monday. A statement from the Chairman of the Verkhovna Rada, Andriy Parubiy, offered support.

The Russian aggression against Ukraine has continued for some five years. The Crimea and part of the Donetsk and Luhansk regions have been occupied. It is nearly every day that our military positions are shelled or machine-gunned by Russian terrorists in the Donbas. It is obvious, the front of the Russian aggression has expanded and now it reaches the Black and Azov Seas.

NATO Secretary General, Jens Stoltenberg, voiced support for Ukraine’s right to its territorial waters.