The Ukrainian Parliament Thursday voted to withdraw from a wide-ranging treaty on friendship with Russia, the latest step in escalating tensions between the two neighboring countries.

The Supreme Rada overwhelmingly supported a motion by President Petro Poroshenko not to prolong the treaty when it comes up for renewal in April.

The camouflage-clad president visited an air base to announce an upcoming dispatch of troops to the Russian border.

The long-simmering conflict between Russia and Ukraine that started with Russia’s annexation of Crimea in 2014 spilled into the open on Nov. 25 when the Russian coast guard fired upon and seized three Ukrainian naval vessels and their crews. The seamen are still in Russian captivity. Ukraine’s foreign minister reiterated his country’s call for the release and safe return of the 24 Ukrainian sailors.

Pavlo Klimkin in a speech at the Organization for Security and Cooperation in Europe warned that since the Crimean annexation Russia has not pulled back but, on the contrary, has extended operations into the Black Sea and the Sea of Azov, AP reported.

With the Ukraine-Russia conflict at the top of the OSCE agenda, the EU’s High Representative Federica Mogherini Thursday also called on Russia to release the Ukrainian ships and soldiers “without delay.”

Poroshenko responded to the standoff by introducing martial law for 30 days, something Ukraine hadn’t done even after Crimea’s annexation and amid large-scale fighting between Ukrainian forces and Russia-backed separatists in 2014-15.

As part of martial law, Ukraine has beefed up its forces on the border with Russia, called up reservists for training and barred entry to all Russian males aged between 16 and 60.

Poroshenko in an opinion piece published in The New York Times Thursday called on the West to respond to what he described as Russia’s aggression by imposing additional sanctions on the Kremlin.

“Our common task is not to allow Russia to spill its aggression into the Sea of Azov,” he said.

“While the West is speaking, Mr. Putin is acting. It is time to respond.”

Poroshenko visited a military air base in the city of Zhytomyr where Ukraine’s Air Assault Forces troops were preparing to leave for the locations on the border with Russia “in order to strengthen our defense capabilities and be ready to stop the aggressor without losing a second.”

The Ukrainian Parliament voted not to prolong the friendship treaty with Russia, which is up for renewal next April, and adopted a bill that unilaterally doubles the extent of Ukraine’s territorial waters to 24 nautical miles.

Ukrainian authorities say this will allow the coast guard and the navy to be more efficient in patrolling the area to prevent military threats and smuggling. The bill also allows Ukrainian border guards to open fire without warning on potential attackers.