Russian President Vladimir Putin has accused Ukraine of choosing terror over peace following "attacks" in Crimea that he says were orchestrated by Ukrainian military and intelligence forces.
"The attempt to provoke an uptick in violence, to provoke conflict is nothing but an attempt to distract public attention," Putin said in a press conference in Moscow on Wednesday.
"We will, of course, do everything to assure the security of infrastructure, citizens and will take additional measures to provide security, including serious additional measures," he said.
But, Ukrainian President Petro Poroshenko rejected Putin's claims, calling them "equally cynical and insane." He said, "We would never ever use terror to de-occupy Crimea."
"Ukraine is devoted to restore its sovereignty and territorial integrity exclusively through political and diplomatic means. That includes [the] de-occupation of Crimea," Poroshenko said Wednesday.
The FSB says it foiled "terrorist attacks" in Crimea by Ukrainian military and intelligence forces during the weekend. The security agency says two of its officers were killed during the clashes with groups it says were sent by the Ukrainian defense ministry.
Authorities say they found 20 homemade explosives, ammunition and mines in the area of the attack.
In a statement, the FSB said "the aim of the sabotage and terrorist attacks was to destabilize the social and political situation" ahead of next month's elections in Russia and Crimea.
It said several Russian and Ukrainian citizens were detained, including one it identified as a Ukrainian intelligence officer.
Russia annexed Crimea from Ukraine in 2014 following the ouster of Kremlin-backed president Viktor Yanukovych following pro-EU demonstrations.