An airstrike destroyed an apartment building in eastern Ukraine Tuesday, killing at least 11 people and triggering new accusations of direct Russian involvement in Ukraine's ongoing battle against pro-Russian rebels.
Details surrounding the strike in the town of Sniznhe remained murky late Tuesday, hours after separatists blamed Ukraine's air force for the attack.
Ukraine military spokesman Andriy Lysenko denied Ukrainian involvement, saying no military planes had flown in the east since Monday. He said "the [Sniznhe] flight can only be described as a cynical provocation" - a thinly veiled accusation against Russia. Kyiv also accuses the Russian military of downing a Ukrainian military transport plane Monday near Luhansk. Moscow has not commented.
Earlier Tuesday, as regional tensions soared, a top Ukrainian defense official said Kyiv has "absolute proof" that Russia was involved in downing the Ukrainian plane.
General Mykhaylo Koval - in comments to Ukrainian television - did not elaborate. But he cited evidence of a new Russian troop buildup on the border, saying "Ukraine, as never before, is on the threshold of large-scale aggression by its northern neighbor."
On Monday, NATO confirmed the Russian buildup. A spokesman told VOA that 10,000 troops, including special forces, are marshaled in border areas, along with tanks, artillery and supply vehicles. That is about a tenfold increase in the past month.
Fighting has surged in the east since the Ukrainian government refused to renew a unilateral cease-fire June 30. Since then, Ukrainian forces have driven the rebels out of several cities, including their main stronghold of Slovyansk.
In a related development, Moscow invited diplomats from 18 countries to visit a Russian border town where it says cross-border Ukrainian shelling killed one person Sunday.
Russia's Foreign Ministry described the shelling as "an aggressive act" that could have "irreversible consequences." Ukraine denies involvement.
The Russian daily Kommersant quoted an unnamed source Monday as saying the Kremlin is considering "pinpoint retaliatory strikes" against Ukraine in response to the shelling. However, the office of President Vladimir Putin called such reports "nonsense."
VOA's Anita Powell reports from Sumy region, Ukraine, along the Ukrainian-Russian border:
SUMY REGION - UKRAINE - Ukrainian officials are tightening security at the border with Russia, amid continued clashes with pro-Russian separatists. Even at places on the border far from the fighting, trenches have been dug and other preparations made to defend against a feared Russian onslaught.
As Ukrainian troops continue to battle pro-Russian separatists, tensions are high along the nation’s 2,000-kilometer land border with Russia.
Here, in a remote border post near the city of Sumy, cross-border traffic has slowed -- and trenches have been dug in preparation for an invasion. These four-meter wide ditches are meant to stop Russian tanks.
This idyllic rural border post in northeastern Ukraine is far from the eastern flashpoints of Donetsk and Slovyansk.
The head of the Yunakivka border post, Major Yuriy Mikhailyuk, says they’re not taking any chances after Russia violated Ukrainian airspace in June.
“If you look on the left of the state border, 500 meters from the place where you’re filming, you’ll see the place where a Russian helicopter violated the airspace of Ukraine. It flew about 2.5 kilometers and returned to Russia," said Mikhailyuk.
In the town of Sumy, which has long had close ties to nearby Russian towns, regional governor Volodymyr Shulga says the government has taken several steps to keep its residents safe.
“We’ve tightened the control of the law enforcement authorities and border forces. Plus, we’ve excavated more than 25 kilometers of a four-meter by two-meter ditch on the border with the Russian Federation," said Shulga.
Sumy's strongly nationalistic residents say they are on guard for any outbreak of pro-Russian separatist sympathies.
Dmytro Lantushenko, who heads the region’s department of youth and sport, says the town’s pro-Ukrainian spirit will keep it safe.
“I’m absolutely sure that we really don’t have any separatist sentiment in the Sumy region today. Moreover, the level of patriotism among youth and students runs high," said Lantushenko.
At the border, business is slow. Cars and pedestrians used to cross over frequently. Nowadays, the crossing is frequented only by the border guards.
On a recent visit, though, tensions were evident.
As VOA News began to film in the space between the border posts, this plume of smoke rose in front of the Russian post.
That was the extent of the action at this sleepy border post during a recent visit.
But as the smoke clouds billow, so too does Ukraine’s fears of its larger, better-armed neighbor.