By Polina Nikolskaya and Darya Korsunskaya
MOSCOW, (Reuters) - Russian President Vladimir Putin on Wednesday accused Ukrainian President Petro Poroshenko of orchestrating a naval "provocation" in the Black Sea at the weekend in order to boost his flagging popularity ratings before an election next year.
Russia seized three Ukrainian naval vessels and their crews on Sunday over what it said was their illegal entry into Russian waters, something Ukraine denies.
The episode has raised fears in the West of a wider conflict between the two countries and Kiev has since introduced martial law in parts of the country, saying it fears a possible Russian invasion.
Some of Ukraine's Western allies have raised the possibility of imposing new sanctions on Russia over the incident, which could deliver a blow to the Russian economy.
In his first public comments on the incident, Putin said the Ukrainian vessels had clearly been in the wrong, dismissed the incident as a minor border issue, and accused Ukrainian President Petro Poroshenko of having orchestrated the mini crisis in order to boost his dire ratings.
"It was without doubt a provocation," Putin told a financial forum in Moscow.
"It was organised by the president ahead of the elections. The president is in fifth place ratings-wise and therefore had to do something. It was used as a pretext to introduce martial law."
Ukraine was successfully using the episode to sell anti-Russian sentiment and the West was ready to forgive Ukrainian politicians their shortcomings because it bought into the narrative Kiev was promoting, said Putin.
The Russian leader was speaking after Moscow said it would send more of its advanced S-400 surface-to-air missile systems to Crimea, the Ukrainian region it annexed in 2014, and a Reuters reporter saw a Russian warship deploying nearby as tensions with Ukraine rose.
Fallout from the episode risks derailing a meeting between U.S. President Donald Trump and Putin at a G20 summit in Argentina later this week. Trump said on Tuesday that he might cancel the meeting due to the incident, but Putin said on Wednesday he still hoped to meet Trump.
(Additional reporting by Tom Balmforth, Polina Ivanova, Vladimir Soldatkin, Katya Golubkova, Gleb Stolyarov and Oksana Kobzeva in Moscow; Writing by Andrew Osborn; Editing by Christian Lowe)