Ukrainian lawmakers voted on Monday to back a proposal by President Petro Poroshenko to introduce martial law for a period of 30 days in areas of the country most vulnerable to an attack from Russia.
They also voted to confirm that Ukraine would hold presidential elections on March 31.
The vote followed the capture of three Ukrainian vessels by Russia over the weekend, a crisis that threatened to pitch the two countries into open conflict.
Ukrainian navy ships in the Kerch Strait near Crimea have been fired on by Russia, Ukraine says. Source: AAP
Separately, the International Monetary Fund said introducing martial law would have no bearing on continued IMF cooperation with Ukraine.
Russia's response
Russian Foreign Minister Sergei Lavrov on Monday accused Kiev of "dangerous" moves in the Kerch Strait after a confrontation between Russian and Ukrainian navy ships.
Lavrov said Ukraine had violated international norms with "dangerous methods that created threats and risks for the normal movement of ships in the area".
Lavrov called the incident a "clear provocation" by Kiev and accused the European Union of "blind support" for Ukraine.
"We call on Kiev's Western sponsors to calm those who are trying to earn political points on military hysteria," he said, implying the incident was planned ahead of Ukraine's presidential election next year.
Britain, US condemns Russia
Britain on Monday condemned Russia's "act of aggression" against Ukrainian ships in the Kerch Strait off the coast of the Kremlin-annexed Crimea peninsula.
"We condemn Russia's act of aggression in seizing three Ukrainian vessels and their crew," a Downing Street spokesman said.
"This incident provides further evidence of Russia's destabilising behaviour in the region and its ongoing violation of Ukrainian territorial integrity."
Downing Street did not immediately address the issue of punitive measures against Moscow.
But Foreign Secretary Jeremy Hunt accused Russia if flouting international law.
"Once again, we see Russian contempt for international norms and Ukrainian sovereignty," Hunt said in a message posted on Twitter.
"Russia must release detained Ukrainian sailors and guarantee free passage through Kerch Straits."
The Ukrainian navy says six men were wounded when Russian coast guards opened fire on three ships. Source: AAP
Meanwhile, the United States on Monday warned Russia that "outlaw actions" like the seizure of Ukrainian ships in the Sea of Azov are preventing normal relations from developing between Washington and Moscow.
US Ambassador Nikki Haley told an emergency meeting of the UN Security Council that "the United States would welcome a normal relationship with Russia. But outlaw actions like this one continue to make that impossible."
Haley put the blame firmly on Russia for the clash, calling the seizure of the ships an "outrageous violation of sovereign Ukrainian territory" and slamming "yet another reckless Russian escalation."
But she did not threaten further sanctions, instead calling for a de-escalation of tensions.
Haley said her remarks were agreed following conversations with President Donald Trump and Secretary of State Mike Pompeo and reflect "concerns at the highest level of the American government."
The US warning comes days ahead of a planned meeting between Trump and his Russian counterpart Vladimir Putin, on the sidelines of the G20 summit in Argentina later this week.
