The Ukrainian government says its forces have retaken two more eastern cities from pro-Russian rebels.
The website of Ukrainian President Petro Poroshenko said the national flag was raised in Artemivsk and Druzhkivka.
It comes a day after government forces regained control of the rebel stronghold of Sloviansk.
Meanwhile, large crowds have attended a rally in the regional capital, Donetsk, in support of the rebels.
Rebel fighters have re-grouped in Donetsk and are reported to have attacked the state prison guard headquarters in an attempt to seize weapons.
Despite their recent losses, the rebels still hold the regional capitals of Donetsk and Luhansk and other key areas.
However, senior Ukrainian security official Mykhaylo Koval said Luhansk and Donetsk would now be besieged until separatist forces there surrendered.
"There is a clear strategic plan, which has been approved. These cities will be completely blockaded," he said.
"These measures will result in the separatists - let us call them bandits - being forced to lay down arms."
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