MOSCOW (AFP) - Russian President Vladimir Putin on Thursday (Aug 11) moved to ramp up security on the annexed Crimea peninsula after accusing Ukraine of attempting armed incursions into the disputed region, allegations denied fiercely by Kiev.
Russia's FSB security service on Wednesday said it had earlier this week thwarted "terrorist attacks" in Crimea by Ukrainian military intelligence and beaten back armed assaults.
The allegations have ratcheted up tensions in a feud sparked by Moscow's 2014 seizure of the Black Sea peninsula from Ukraine and prompted fears of possible wider conflict.
Putin held a meeting with his 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 security service said Wednesday that 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 then accused the authorities in Kiev of "practising terror" and warned 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." Ukrainian President Petro Poroshenko hit back that Moscow's claims were "senseless and cynical".
"These fantasies are only another pretext for the next military threats toward Ukraine," his office quoted him as saying.
Two residents living close to the Ukraine-Crimea frontier told AFP that there has been an unexplained build-up of Russian military hardware in the area over the past few weeks.
A senior Ukrainian security official told AFP on Thursday that the claims from Moscow were a "crude Russian provocation" and that Kiev was "getting ready for anything," including an invasion.
Russia says it has detained several Ukrainian and Russian citizens over the incident, including an alleged Ukrainian military intelligence officer called Yevgen Panov. Kiev has called Panov a "hostage".
Moscow and Kiev have been locked in a bitter feud since the Kremlin seized Crimea from Ukraine in March 2014 after Russian-backed president Viktor Yanukovych was ousted.
The crisis has sent ties between Moscow and the West to their lowest point since the Cold War.
The fresh war of words over the alleged incident represents the most serious increase in tensions in months as a separatist conflict in two other regions in east Ukraine - that Kiev and the West blame on Moscow - drags on despite a stalled peace deal.
Putin said a mooted meeting with Poroshenko and mediators German Chancellor Angela Merkel and French President Francois Hollande at next month's G20 summit in China was now "senseless".
Independent Russian daily Vedomosti wrote in an op-ed entitled "a new old enemy" that Moscow has tended to ramp up tensions ahead of negotiations over Ukraine.
"The main political question now is what is the future of the Minsk process," the paper wrote, referring to the peace deal hammered out in the Belarussian capital in February 2015.
"Will Russia bring an end to it or demand new concessions?"