Russia Accuses Ukraine Of 'Terrorist' Attack In Crimea

President Vladimir Putin says he'll beef up Russia's military force in Crimea, after Russia's security service claimed that it thwarted a would-be terrorist incursion from Ukraine over the weekend.

The Federal Security Service, the FSB, said that teams of commandos from Ukraine's defense forces made two attempts to enter the Black Sea peninsula, with the intention of sabotaging vital infrastructure. The FSB said Ukrainian forces attempted to cover the infiltration by directing heavy fire at the Russian side, killing two Russian servicemen.

Ukrainian President Petro Poroshenko dismissed the Russian claims, calling them "fantasy" and a "provocation." Poroshenko issued a statement saying that Ukraine would never use terrorism to regain its occupied territory.

The U.S. ambassador to Ukraine, Geoffrey Pyatt, said the U.S. "has seen nothing so far that corroborates Russian allegations of a Crimea incursion."

Russia's President Putin accused Ukrainian authorities of resorting to terror, instead of seeking to solve problems through negotiations. "This news is very alarming, indeed," Putin said. "Our special services have prevented a reconnaissance and sabotage group of the Ukrainian Defense Ministry from getting into Crimea."

So far, Russian officials have not addressed the question of why, if Russian forces were so severely attacked, the Kremlin waited three days to make the allegations.

The Russian defense ministry announced the Russian navy will conduct exercises in the Black Sea intended to protect Crimea from underwater saboteurs.

Putin said it would be "pointless" to hold another round of peace talks under the so-called "Normandy Format," because Ukrainian leaders are not interested in searching for compromises. The Normandy Format brings together the leaders of Ukraine, Russia, Germany and France. Russia had earlier agreed to attend a meeting of those leaders on the sidelines of the G-20 meeting next month in China.

Ukraine's ambassador to the United Nations said his country fears that Russia will use the claims of attempted sabotage as a pretext for further military action against Ukraine. Russia has been building up its forces in Crimea in recent months.

Russia annexed Crimea from Ukraine in March of 2014, after Russian soldiers in unmarked uniforms took control of key government buildings. President Putin initially denied that Russia had deployed soldiers on Ukrainian territory, but later said the troops were necessary to protect people there whose primary language is Russian.

Russia claims that Crimean citizens requested to be part of Russia following a hastily-organized referendum. Few other nations have recognized the legitimacy of that vote, which was conducted without international monitoring.