Kiev: Ukraine on Thursday placed its forces around Crimea on high alert as tensions soared after Moscow accused Kiev of attempting armed incursions into the disputed peninsula.
Russia's FSB security service said yesterday it had thwarted "terrorist attacks" in Crimea this week by Ukrainian military intelligence and beaten back armed assaults, but Kiev fiercely denied the claims.
The allegations ratcheted up the heat in a feud sparked by Moscow's 2014 seizure of the Black Sea peninsula from Ukraine and raised fears of possible wider conflict.
The UN Security Council was to discuss the growing tensions later today at the request of Ukraine, a non-permanent council member.
Ukraine's pro-Western President Petro Poroshenko met his top brass and ordered forces along the frontier with Crimea and across the conflict-wracked east onto "high-alert level".
Russian President Vladimir Putin also held a meeting with security chiefs to discuss "additional measures for ensuring security for citizens and essential infrastructure in Crimea," the Kremlin said in a statement.
"Scenarios were carefully considered for anti-terrorist security measures at the land border, in the waters and in the airspace of Crimea," it said.
The FSB said one of its officers was killed in armed clashes while arresting "terrorists" on the night of August 6-7, while a Russian soldier died in a firefight with "sabotage-terrorist" groups sent by the Ukrainian military on August 8.
An irate Putin accused Kiev of "practising terror" and warned that the deaths of the two Russian officers would have consequences.
"We obviously will not let such things slide by," Putin said. "This is a very dangerous game."
Poroshenko hit back, saying Moscow's claims were "senseless and cynical."
"Fantasies are only another pretext for the next military threats toward Ukraine," he said.
Two residents living on the Russian-controlled side of the Crimea-Ukraine frontier told AFP there had been an unexplained build-up of Russian military hardware in the area over the past few weeks.
Russia is holding nationwide legislative elections next month -- including in Crimea -- and the FSB said the alleged raids could be aimed at destabilising the situation ahead of the vote.
A senior Ukrainian security official told AFP that Moscow's claims were a "crude Russian provocation" and that Kiev was "getting ready for anything," including an invasion.