KIEV, Aug. 10 – Tensions between Ukraine and Russia escalated on Wednesday after two Russian servicemen were killed in Crimea as Moscow’s alleged its forces had uncovered a plot to sabotage the peninsula’s infrastructure.

Russian President Vladimir Putin accused Ukrainian special operations troops of sending two teams of plotters to Crimea, and threatened to respond.

“There is no doubt that we will not let these things pass,” Putin said in remarks broadcast on state television.

Ukrainian President Petro Poroshenko dismissed Putin’s accusations as “fantasies,” adding that Moscow is seeking a pretext for serious military escalations.

“These fantasies are just a pretext for another portion of military threats against Ukraine,” Poroshenko said in a statement.

“It is Russia who has been generously funding and supporting terrorism in the territory of Ukraine for a long time and raising it to the level of its state policy,” Poroshenko said.

Russia’s security service FSB said in a statement that one of its officers was killed in armed clashes while arresting the plotters on the night of August 6-7 while a Russian soldier died in a firefight with "sabotage-terrorist" groups sent by the Ukrainian defense ministry on August 8.

Ukraine's national security council chief Oleksandr Turchynov blasted the claims as "hysterical and false" and said Moscow was trying to stoke fear in Crimea.

"Russia is preparing for a planned escalation of the situation and disrupt the Minsk agreements,” Turchynov said.

"In order to go on further escalation of the conflict, Putin has not invented anything better than a cheap theatrical production by FSB with improvised explosive devices," Turchinov said.

"As for terrorism, which Russian President mentioned, the total terror, cynical human rights violations and massacres it has Russia on the occupied territories of Donbas and Crimea,” Turchynov said.

The Organization for Security and Cooperation in Europe monitoring the frontier between mainland Ukraine and Crimea did not report any incidents.

But it said road traffic was halted this earlier this week and border guards appeared to be on "heightened alert".

In its statement, the FSB -- which controls Russia's border guards -- said it had "foiled terrorist attacks on the territory of Crimea prepared by the intelligence directorate of the Ukrainian defense ministry".

"The aim of the sabotage and terrorist attacks was to destabilize the social and political situation" ahead of elections in Russia and Crimea next month, it said.

Fighting in the east between Ukrainian forces and pro-Russian rebels is still rumbling on as a peace deal to end the violence fails to make progress.

Russia is gearing up for nationwide legislative elections on September 18 and Putin has warned his security officials that "foreign enemies" are seeking to disrupt the vote. (nr/ez)