Nov. 28 (UPI) -- Tensions are escalating in the latest dispute between Russia and Ukraine.
The recent spat started Sunday when Russia seized three Ukrainian navy ships and crew in the Kerch Strait. Russian President Vladimir Putin said the ships entered territorial waters illegally to provoke a response. The crisis prompted Ukrainian President Petro Poroshenko to impose martial law in some parts of the country for 30 days.
"It's a provocation initiated by the current authorities, and I think by the [Ukrainian] president, in light of the upcoming elections to be held next year ... The incident in the Black Sea happened, it is a border incident, no more," Putin said at a Moscow business forum, according to CNBC.
Putin went on to say that Poroshenko hopes the crisis will boost his popularity before Ukraine's March election.
Ukraine called it an "act of aggression" by Russia.
Poroshenko warned Putin that if Russia attacks Ukraine, it would pay a "huge price."
Russia is sending new S-400 missile systems to Crimea in response to the increasing threat. The new missile systems, called "Triumf" in Russian, are capable of shooting down aircraft and ballistic missiles from 250 miles away. Three divisions are already in place.
Russia's state-run media said a fourth S-400 missile system will be in place by the end of the year.
U.S. Ambassador to the United Nations Nikki Haley said Russia's actions were an "outrageous violation of sovereign Ukrainian territory"
Analysis by international think tank Chatham House said Putin hopes to undermine the Ukrainian economy to hurt Poroshenko's chances at reelection, according to a Bloomberg report. A Ukrainian revolution overthrew the Kremlin-backed leader in 2014.
Chatham House believes Russia wants to disrupt Ukrainian exports of metal and agricultural goods.
"The situation is affecting local economies along the coast and destabilizing the Ukrainian ports of Mariupol and berdyansk," Chatham House research fellow Mathieu Boulegue said.
Russia faces its own sanctions for annexing the Crimea, also in 2014.