Russian President Vladimir Putin held talks with top security chiefs on Thursday over a "deterioration of the situation" in eastern Ukraine after pro-Russian rebels there accused Kiev of launching a new offensive in violation of a ceasefire.
Sporadic violence has flared since the Sept. 5 truce in a conflict that has cost over 4,000 lives; but the ceasefire has looked particularly fragile this week with separatists and the central government accusing each other of violations.
Andrei Purgin, deputy prime minister of the self-proclaimed Donetsk People's Republic, said the Ukrainian army had launched "all-out war" on rebel positions, Russian news agency RIA said.
Ukrainian military spokesman Vladyslav Seleznyov denied this, saying the army remained in agreed positions.
"We refute these allegations...we're strictly fulfilling the Minsk memorandum (on a ceasefire)," he said by telephone.
A Kremlin statement said the presidential Security Council, which groups key security and defense officials under Putin's chairmanship, discussed among other things a "deterioration of the situation in the Donbass due to repeated violations of the ceasefire by the armed forces of Ukraine."
It did not say what decisions, if any, had been reached over the conflict that broke out in the industrialized east after the overthrow of Ukraine's Moscow-backed leader Viktor Yanukovich in February and Russia's subsequent annexation of Crimea.
A Reuters witness in the rebel stronghold of Donetsk said there was no sign the conflict was escalating.
Representatives of the separatist regions earlier put out a joint statement calling for a redrafting of the Minsk deal, which established a ceasefire in exchange for Kiev granting "special status" to eastern territories.
Rebels say Ukraine has violated the deal by seeking to revoke a law that would have granted eastern regions autonomy. Kiev says this was a consequence of Sunday's separatist leadership elections which it says go against the agreement.
The Ukrainian military said three soldiers had been killed on Thursday, reporting a total of 26 separate artillery clashes with separatists.