Ukrainian war planes have bombarded separatists along a broad front today, according to Kiev, after President Petro Poroshenko said "scores and hundreds" would be made to pay for a deadly missile attack on Ukrainian forces.
In exchanges marking a sharp escalation in the three-month conflict, jets struck at the "epicentre" of the battle against the rebels close to the border with Russia, a military spokesman said.
The planes targeted positions from where separatists using high-powered Grad missiles bombarded an army motorised brigade yesterday, killing 23 servicemen.
Warplanes also struck at targets near Donetsk, the east's main town where rebels have dug in, destroying a powerful fighter base near Dzerzhinsk, Andriy Lysenko, a spokesman for the "anti-terrorist operation" said.
"According to preliminary assessment, Ukrainian pilots...killed about 500 (rebel) fighters and damaged two armoured transporters," Mr Lysenko told journalists.
In an earlier air attack on a base near Perevalsk, north of Donetsk, two tanks, 10 armoured vehicles and "about 500" rebel fighters were destroyed, he said.
Rebel representatives, quoted by Russian news agencies, denied they had suffered big losses and said the Ukrainians were using outdated intelligence about where separatist forces were deployed.
"There were no volunteers (rebels) where the Ukrainian aviation was active yesterday," said a spokeswoman for the Luhansk-based separatists, referring to the Peravalsk attack.
Earlier, the border guard service said jet fighters were scrambled to strike at the pro-Russian separatists after they resumed missile attacks on government forces deployed near the frontier with Russia, south-east of the city of Luhansk.
In the military action, which began on Friday evening and continued today, five Ukrainian servicemen were killed, Lysenko said. There had been 16 over-flights by Ukrainian fighter jets in all, he said.
Rebels had also carried out mortar and missile bombardment of army checkpoints at Dyakove and Nyzhnoderevechka near Luhansk, the "anti-terrorist operation" said.
Journalists based in Donetsk said Ukrainian forces appeared to have shelled Maryinka, a suburb, on Friday night. Tenmulti-storey apartment blocks bore traces of fire and parts ofshells could be seen in the street.