Pro-Russian separatists in Ukraine are reported to be regrouping in Donetsk after government forces retook some of their main strongholds.
President Petro Poroshenko said the recapture of the rebels’ stronghold of Sloviansk on Saturday was of “huge symbolic importance”.
But he warned it was too early for celebrations.
Despite recent losses, the rebels still hold the regional capitals of Donetsk and Luhansk and other key areas.
Sloviansk had been considered a focal point of the rebellion, and was the military centre of the self-declared separatist People’s Republic of Donetsk.
But on Saturday, rebels left the city following a night of mortar shelling apparently orchestrated by the breakaway region’s military commander, Igor Strelkov.