Ukrainian President Pyotr Poroshenko on Monday, November 26 enacted the National Security and Defense Council’s decision to declare martial law until January 25, 2019, says a document published on the presidential website, according to TASS.

"The National Security and Defense Council’s decision concerning ‘emergency measures to ensure Ukraine’s state sovereignty and independence and declare martial law in Ukraine’ is hereby enacted," the document reads.

According to the Russian Federal Security Service (FSB), on Sunday morning, three ships from the Ukrainian Navy - the Berdyansk, the Nikopol and the Yany Kapu - crossed Russia’s border. The three vessels were ultimately detained in Russia's waters.