KIEV, Aug. 11 - Vladimir Putin summoned his security council and the Russian Navy announced war games in the Black Sea a day after the Russian president accused Ukraine of trying to provoke a conflict over Crimea, which Moscow seized and annexed in 2014, Reuters reported.

The belligerent posture heightened worries in Ukraine that Russia may plan to ramp up fighting in a war between Kiev and pro-Russian eastern separatists that had been de-escalated by a shaky peace process.

Using some of his most aggressive rhetoric against Kiev since the height of the war two years ago, Putin has pledged to take counter-measures against Ukraine, which he accused of sending saboteurs into Crimea to carry out terrorist acts.

Ukraine has called the accusations false and says they look like a pretext for Russia to escalate hostilities.
Such an escalation could be used by Putin to demand better terms in the Ukraine peace process, or to inflame nationalist passions at home ahead of Russian parliamentary elections next month.

The Russian leader met his top military and intelligence service brass on Thursday and reviewed "scenarios for counter-terrorism security measures along the land border, offshore and in Crimean air space," the Kremlin said.

President Petro Poroshenko said he had ordered all Ukrainian units near Crimea and in eastern Ukraine onto the highest state of combat readiness. He was seeking to urgently speak to Putin, the leaders of France and Germany, U.S. Vice President Joe Biden and European Council President Donald Tusk.

In Washington, State Department spokeswoman Elizabeth Trudeau said the United States was extremely concerned and called on both sides to reduce tension and rhetoric.

In New York, the U.N. Security Council held a closed-door meeting at Ukraine's request to discuss the growing tensions.

Ukrainian U.N. Ambassador Volodymyr Yelchenko warned that Russia had amassed more than 40,000 troops in the region and said the build-up could reflect "very bad intentions."

Russia says it caught infiltrators after at least two armed clashes on the border between Crimea and Ukraine over the weekend, and one of its soldiers and an FSB security service employee were killed. Kiev denies the events ever happened.

U.S. ambassador to Ukraine Geoffrey Pyatt said Washington had so far seen nothing to corroborate Russia's version. A spokeswoman for EU foreign affairs chief Federica Mogherini also said there had been no independent confirmation.

Whatever the truth, the allegations have already scuppered planned talks about eastern Ukraine slated for the sidelines of a G20 summit in China next month. Putin said such talks would now be "pointless."

In an editorial, the Russian newspaper Vedomosti said escalation was a proven Kremlin tactic ahead of negotiations. Putin was trying either to alter or to tear up the Minsk peace process, named for the Belarus capital where truces were hammered out for the war in eastern Ukraine's Donbas region.

"Events in Donbas in 2014-15 showed that the Kremlin tactic is to raise the stakes before negotiations. The main political question now is what will happen to the Minsk process. Will Russia break away from it or will it demand new concessions?" the newspaper wrote.

"Putin in his rhetoric has returned to the start of 2014. Once again, he does not deem the Ukrainian authorities legitimate."

The European Union and the United States have tied the success of talks under the Minsk process to any possible decision to lift financial sanctions imposed on Russia over the Ukraine crisis.

But Moscow has grown increasingly frustrated by the talks and by what it says is Ukraine's refusal to fulfill the terms of the truce. Kiev for its part says Moscow is the one that is still stirring tensions among pro-Russian separatists.

Escalating tension over Crimea could give Putin a pretext to abandon talks altogether, or demand changes to their format and terms, while holding out the prospect of a full-scale renewal of hostilities if he doesn't get what he wants.

It could also help rally Russians ahead of the parliamentary vote, in which the main pro-Kremlin United Russia Party might struggle to win as many votes as usual because of an economic slump caused by low oil prices as well as the sanctions. (rt/ez)