Pleas for calm as Russia, Ukraine square off

KIEV, Ukraine – World powers urged Russia and Ukraine to refrain from ratcheting up a confrontation over Crimea after President Vladimir Putin blamed Kiev for "terror" activities on the disputed peninsula and threatened to retaliate.

The European Union said Friday that there was no independent confirmation of claims that Ukrainian troops had killed two Russian servicemen in Crimea, which Putin has warned would bring a "very serious" response.

Russia has deployed an advanced S-400 surface-to-air missile battery to the Crimean Peninsula amid the escalating tensions, according to Russian news reports. The missile system, once operational, would be able to target aircraft deep into Ukrainian airspace.

The 28-member E.U. called on both sides to refrain from intensifying what has become the worst diplomatic standoff between the countries since a 2015 truce eased hostilities in Ukraine's separatist conflict.

"We reiterate our condemnation and nonrecognition of the illegal annexation of Crimea," European Commission spokesman Alexandre Polack said Friday. "There has been neither concrete evidence provided by Russia sustaining its claim nor any independent confirmation of the claims made by Russian authorities."

The confrontation coincides with a surge in violence in Ukraine's eastern Donbas region, where government troops are fighting rebels who Kiev says are getting cash, weapons and fighters from Russia.

The flare-up torpedoed plans to revive four-way peace talks at the September G-20 meeting in China and raised warnings from analysts of a potential military conflict before Russia's September parliamentary elections.

On Thursday, Putin discussed bolstering Crimea's defenses with his security council. Russia may cut diplomatic ties with Ukraine, recalling embassy staff, the newspaper Izvestia said Friday, citing an unidentified person in Russian foreign-policy circles.

Ukrainian President Petro Poroshenko dismissed Russia's accusations as "fiction" that could be an "excuse for further military threats" against his country. He put the military on alert along the contact line with separatist forces and the Black Sea territory, where Ukrainian officials say that Russian troops are reinforcing their positions.

International monitors for the Organization for Security and Cooperation in Europe registered a sharp increase in cease-fire violations in the Luhansk region. OSCE drones spotted multiple-launch rocket systems in both rebel-held and government-controlled areas, Alexander Hug, deputy chief of the OSCE mission in Ukraine, said in a conference call Friday.

Pro-Russian separatists attacked Ukrainian forces near separatist-held cites of Donetsk and Luhansk and the Black Sea port of Mariupol, held by government troops, overnight Thursday, Ukraine's military said. One Ukrainian soldier was killed and four were injured, according to spokesman Oleksandr Motuzyanyk.

Western countries have refused to recognize Russia's takeover of Crimea. They have imposed sanctions that have helped force the world's biggest energy-exporting economy into recession over the annexation and the conflict in eastern Ukraine, which the United Nations says has killed almost 10,000 people.

Putin has exhibited a tendency to use instability in the region as leverage in negotiations. He also has launched military operations while the world's attention is on the Olympic Games and many leaders are on vacation. The annexation of Crimea came just after Russia hosted the Sochi Olympics, and Russia sent troops into Georgia during the 2008 Beijing Olympics.

The deployment of the truck-mounted missile system had been planned at least since July, but its arrival in Crimea coincided with the flurry of military activity and rhetoric.

The S-400 can hit targets well over 150 miles from its launch site when paired with the appropriate radar array and is billed as one of Russia's most advanced surface-to-air defense systems. The Crimean peninsula is currently home to the older S-300 Russian surface-to-air missiles that will probably be replaced by the arrival of the newer S-400s.

Between Aug. 6 and Aug. 8, the Russian Federal Security Service, or FSB, said that it arrested Ukrainian saboteurs who had sneaked over the border, and also recovered a large cache of explosives in the town of Armyansk. During the arrest, one FSB agent was killed in an exchange of gunfire with the Ukrainian agents, said a statement on the FSB's website. The FSB also claimed to have repelled Ukrainian special forces attempting to infiltrate Crimea in a subsequent cross-border shelling, and said that one Russian soldier was killed.

Eyewitness accounts to the incident have been spotty, and social media reports indicate that there were internet outages in northern Crimea during the FSB operation. The Ukrainian government has denied that it condoned any type of border incursion or that it had shelled Russian forces from its territory.

The month of August usually coincides with an uptick in Russian military training activity. Videos on social media have shown significant numbers of armored vehicles, air defense systems and anti-ship missiles flowing into Crimea from Russia on rail cars and on highways. Ukrainian forces have also reported unusual activity along their front lines in eastern Ukraine where they have been fighting Russian-backed separatists since April 2014.

The surge in activity has put Ukrainian forces on high alert in anticipation of a possible offensive, though since Ukrainian lines have remained mostly unchanged since early 2015, rumors of breakthroughs and large-scale attacks are an almost monthly occurrence.