Ukraine yesterday accused Russian army officers of fighting alongside separatists in the east of the country, and said Moscow was once more building up its troops on the border.
A missile that brought down a Ukrainian transport plane carrying eight people near the border was probably fired from Russia, Ukrainian officials said.
Ukraine’s president, Petro Poroshenko, held an emergency meeting of his security chiefs after a weekend of Ukrainian air strikes on rebel positions near the border with Russia, and charges by Moscow that Kiev killed a Russian man with a cross-border shell.
The intense fighting, during which Ukrainian forces said they inflicted heavy losses on the rebels, marked a sharp escalation in the conflict.
Mr Poroshenko said: “Information has … been confirmed that Russian staff officers are taking part in military operations against Ukrainian forces.”
On Sunday he made similar complaints about Russian incursions to the European Union, aiming to push the bloc to exert greater pressure on Moscow.
Mr Poroshenko told his security chiefs that government forces were now facing a new Russian missile system and there would have to be a change in tactics.
Accusing Russia of embarking on a course of escalation in Ukraine’s eastern regions, National and Security Council spokesman Andriy Lysenko said: “In the past 24 hours, deployment of [Russian] units and military equipment across the border from the Sumy and Luhansk border points was noticed. The Russian Federation continues to build up troops on the border.”
Independently, Nato said Russia had increased its forces along the border to about 10,000-12,000 troops.
The raised again the prospect of Russian intervention, after weeks in which the country’s president, Vladimir Putin, had appeared intent on disengaging, pulling back tens of thousands of troops from the frontier.
The Ukrainian army said it had broken a rebel encirclement of Luhansk airport on Sunday night. A spokesman for the pro-Russian so-called Luhansk People’s Republic said 30 volunteer fighters had been killed by Ukrainian fire on Oleksandrivka, a village to the east of the town.
As military action continued yesterday near the rebel-controlled border town of Luhansk, Ukraine’s defence minister said a Ukrainian AN-26 transport plane, taking part in the military campaign against the rebels, had been shot down by a rocket which was “probably” fired from Russian territory.
Mr Lysenko also rejected Russian charges that Ukrainian forces had fired a shell over the border on Sunday, killing a Russian man. Moscow has described the incident as an “aggressive act” which would have “irreversible consequences”.
Russia said it had invited monitors from the OSCE, a European security and rights body, to visit two of its border crossings as a sign of goodwill.
In a weekend of fierce combat, Ukraine said it had inflicted heavy losses on pro-Russian separatists in air strikes on their positions, including an armoured convoy which Kiev said had crossed the border from Russia.
Mr Poroshenko’s office said Kiev would present documentary proof of incursions from Russia to the international community via diplomats.
Hundreds of rebels, led by a self-proclaimed defence minister from Moscow, have retreated to the Ukrainian city of Donetsk, built reinforcements and pledged to make a stand. The once-bustling city has been emptying in fear of a battle.
Rebel fighters on Monday were evacuating about 200 Donetsk residents by bus across the border into the Rostov area.
Vladimir, 55, a coal miner, said he was sending his wife and two children to stay with relatives across the border. He said: “The Ukrainians have already cut off water. Electricity is only just working. How can you live without water and light?”