Fighting raged in eastern Ukraine for a second day as the army rolled out an offensive against pro-Russia separatists holding the city of Slovyansk, with dead and wounded on both sides, the Ukrainian government has said.
On Tuesday, rebels in the town said they had brought down an armed aircraft and a helicopter, but this was denied by Ukrainian authorities.
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Twelve hours after Kiev's forces launched an overnight military operation in and around the separatist stronghold, where a military helicopter was shot down last week killing 14 servicemen, Vladyslav Seleznyov, a spokesman for the Ukrainians, said: "Today we have had two killed and 42 wounded."
He said that at least 300 people were dead or wounded on the separatist side, but Reuters news agency said that the number could not be independently verified.
Seleznyov told Reuters on Tuesday that fighting was ongoing.
Meanwhile, Ukraine also announced on Tuesday that a total of 181 people, including 59 servicemen, had been killed "by terrorist activity" since hostilities broke out in April.
The fighting in Slovyansk followed a day-long fire-fight on Monday in Luhansk, a town further to the east on the border with Russia, after an attack by separatists on a border guard camp.
At least two people were killed in the city centre of Luhansk, which like Slovyansk is under separatist control, by a blast which rebels said came from a Ukrainian air strike but which the Ukrainians said was caused by a misfire of a heat-seeking missile by the rebels.
Al Jazeera's John Wendle reported heavy firing and bombings on the outskirts of the city, and that the area was blocked by the Ukrainian army
Seleznyov said: "At the present time the active phase of the 'anti-terrorist Slovyansk is going on near Slavyansk. The (separatist) fighters are being blocked. If they refuse to lay down their arms they will be destroyed."
"Our job is to establish peace in the region and this we will do," added the spokesman for the military operation.
"Information that Ukrainian planes and helicopters have been shot down are not true. Yesterday one of the helicopters received holes from small arms fire," he said.
President-elect Petro Poroshenko called for a resumption of military operations by government forces to quell rebellions by pro-Russian fighters across the Russian-speaking east after scoring a resounding election victory on May 25.
The Kiev government says the fighting is fomented by Moscow, which opposes its pro-Western course. Kiev also accuses Russia of letting volunteer fighters cross into Ukraine to fight alongside the rebels.
Moscow denies this and is urging Ukraine to end military operations and open dialogue with the separatists.
Since government forces resumed their push against the rebels, there have been clashes in and around the main industrial hub of Donetsk and near the border town of Luhansk with loss of life on both sides.
But it is unclear whether the Ukrainian military, backed up by attack aircraft, is making real progress against the rebels, who are occupying strategic points in densely populated cities, Reuters reported.
With violence continuing in Ukraine's east and tension high between Ukraine and Russia, the crisis is certain to dominate diplomatic exchanges when the newly-elected Poroshenko meets world leaders this week ahead of his inauguration next Saturday.
He is expected to meet US President Barack Obama and other European leaders in Warsaw on Wednesday and will see Russia's Vladimir Putin at World War Two D-day celebrations in France on Friday, though no formal talks are planned.