Ukraine scrambled jet fighters to strike at rebel positions early on Saturday, after separatists resumed missile attacks on government forces near the frontier with Russia, the border guard service said.
In a night of violence in several areas of eastern Ukraine following a missile strike by separatists on Friday that killed at least 23 government servicemen, Ukrainian forces also used artillery to respond to rebel fire, the military said.
Ukrainian President Petro Poroshenko had pledged to "find and destroy" the pro-Russian rebels responsible for the missile attack at Zelenopillya, which also wounded nearly 100.
At least two more Ukrainian soldiers were killed and about 20 injured on Saturday in a mortar and missile bombardment by the rebels of army checkpoints at Dyakove and Nyzhnoderevechka near Luhansk, the government's "anti-terrorist" operation said.
Luhansk, like the main industrial city of Donetsk, is controlled by pro-Russian separatists who set up 'people's republics' in Russian-speaking areas and declared a wish to join Russia in response to a pro-Western revolt in the capital Kiev.
Rebel fighters meanwhile said that Ukrainian fighter planes had carried out air strikes on Saturday in the eastern town of Horlivka.
"There were a series of powerful explosions. Details are being clarified," a separatist representative, Konstantin Knyrik, was quoted as saying by Russia's interfax news agency.
The Grad missile strike on Friday on a motorized brigade at Zelenopillya was one of the deadliest against government forces in three months of fighting since the separatist rebellions erupted following Russia's annexation of Crimea.
Poroshenko, whose forces had recently seemed to be prevailing over the rebels, said they would pay for the strike in their "scores and hundreds".
The border guard service in a statement said army and border guard units had again come under missile attack in several areas near the border just after midnight.
"The Ukrainian armed forces returned artillery fire. On the defense minister's order, fighter jets went up to patrol Ukraine's air space and be ready to deflect further possible attacks," it said.
EU names Ukraine rebel leaders hit with sanctions
The European Union targeted Ukrainian separatist leader Aleksandr Borodai and 10 other rebels with travel bans and asset freezes on Saturday, avoiding fresh sanctions on Russian business to avoid antagonising its main energy supplier.
The EU said Borodai was "responsible for the separatist 'governmental' activities of the so-called 'government of the Donetsk People's Republic'", referring to the city where the military is fighting pro-Russian separatists.
Borodai, a 41-year-old Russian citizen, told a news conference in May he was a political advisor who helped Russia's annexation of the Ukrainian peninsula of Crimea in March and then moved to eastern Ukraine to help separatists there. He denies any links to Moscow.
REUTERS