KIEV, Ukraine - An Air Force fighter jet has been shot down by an air-to-air missile fired from a Russian plane, a spokesman for Ukraine's Security Council said Thursday.
Andrei Lysenko also said Ukrainian troops had been fired upon by missiles from a village just inside Russia.
Officials in Kiev have recently accused Russia's armed forces of being directly implicated in attacks on Ukrainian troops battling an insurgency near the border.
Lysenko said in a televised briefing that the pilot of the Sukhoi-25 jet that was hit on Wednesday evening was forced to bail out after his jet was shot down. He provided no further details.
Pro-Russia rebels, meanwhile, claimed responsibility for strikes Wednesday on two Ukrainian Sukhoi-25 jets.
The Defense Ministry said the second jet was hit by a portable surface-to-air missile, but added the pilot was unscathed and managed to land his plane safely.
Moscow denies Western charges that is supporting the separatists in Ukraine or sowing unrest in its neighbor.
On Monday, Ukraine said one of its military transport planes carrying eight people was shot down by a missile fired from Russian territory. Security Service chief Valentyn Nalyvaichenko said he had "unconditional evidence" that Russia was involved in downing the craft.
Rebels claimed to have shot that plane down.
The U.S. slapped tougher sanctions against Russia on Wednesday for its actions in Ukraine, prompting a strong reaction Thursday from Russian President Vladimir Putin, who said they will stalemate bilateral relations and hurt not only Russian but also American businesses.
Russia's benchmark MICEX was down 2.6 percent in early afternoon trading Thursday upon news of the sanctions while Russia's biggest oil company, Rosneft, was nearly 5 percent down.
The U.S. sanctions target two major Russian energy firms including Rosneft, a pair of powerful financial institutions, eight weapons firms and four individuals.
The U.S. penalties, however, stopped short of the most stringent actions the West has threatened, which would fully cut off key sectors of Russia's oil-dependent economy. But officials said those steps were still on the table if Russia fails to abide by the West's demands to stop its support for the pro-Russia insurgents.