Ukraine’s president has announced a call-up of reservists amid tensions with Russia.

Relations between the two neighbors have strained further following the Nov. 25 incident in which Russia fired upon and seized three Ukrainian naval vessels and their crews.

Ukrainian servicemen are seen aboard a naval ship in the Azov Sea port in Mariupol, Ukraine, Sunday, Dec. 2, 2018.  Ukraine's leader called on Germany and its allies to boost their naval presence in the Black Sea to deter Russia from further aggression in the region and said Russia was blockading Ukrainian ports on the nearby Sea of Azov. (Gleb Garanich/Pool Photo via AP)
Ukrainian servicemen are seen aboard a naval ship in the Azov Sea port in Mariupol, Ukraine, Sunday, Dec. 2, 2018. Ukraine’s leader called on Germany and its allies to boost their naval presence in the Black Sea to deter Russia from further aggression in the region and said Russia was blockading Ukrainian ports on the nearby Sea of Azov. (Gleb Garanich/Pool Photo via AP)

Ukrainian President Petro Poroshenko responded by introducing martial law for 30 days in much of Ukraine.

Ukrainian servicemen are seen at a naval ship in the Azov Sea port of Mariupol, Ukraine, Sunday, Dec. 2, 2018. Ukraine's leader called on Germany and its allies to boost their naval presence in the Black Sea to deter Russia from further aggression in the region and said Russia was blockading Ukrainian ports on the nearby Sea of Azov. (Gleb Garanich/Pool Photo via AP)
Ukrainian servicemen are seen at a naval ship in the Azov Sea port of Mariupol, Ukraine, Sunday, Dec. 2, 2018. Ukraine’s leader called on Germany and its allies to boost their naval presence in the Black Sea to deter Russia from further aggression in the region and said Russia was blockading Ukrainian ports on the nearby Sea of Azov. (Gleb Garanich/Pool Photo via AP)

Poroshenko said Monday that reservists will be summoned for training as part of martial law. He also said that some military units will be redeployed to strengthen the nation’s defenses.

A Ukrainian border guard checks documents of a woman crossing the border the Ukraine - Russia border in Milove town, eastern Ukraine, Sunday, Dec. 2, 2018. On a map, Chertkovo and Milove are one village, crossed by Friendship of Peoples Street which got its name under the Soviet Union and on the streets in both places, people speak a mix of Russian and Ukrainian without turning choice of language into a political statement. (AP Photo/Evgeniy Maloletka)
A Ukrainian border guard checks documents of a woman crossing the border the Ukraine – Russia border in Milove town, eastern Ukraine, Sunday, Dec. 2, 2018. On a map, Chertkovo and Milove are one village, crossed by Friendship of Peoples Street which got its name under the Soviet Union and on the streets in both places, people speak a mix of Russian and Ukrainian without turning choice of language into a political statement. (AP Photo/Evgeniy Maloletka)

Ukraine and Russia have blamed each other for the naval incident that further escalated the tug-of-war that began in 2014 when Russia annexed Ukraine’s Crimean Peninsula and supported separatist rebels in eastern Ukraine.

Source: The Associated Press

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