A spokesman for President Vladimir Putin on Wednesday denied Ukrainian reports Russia had brokered a "permanent cease-fire" in eastern Ukraine, news agency RIA Novosti reported.
Kremlin spokesman Dmitry Peskov was cited as saying Russia could not have reached such a deal with Ukraine's Petro Poroshenko because it is not a party to the Ukraine conflict.
"Putin and Poroshenko really discussed the steps that would contribute to a ceasefire between the militia and the Ukrainian forces. Russia cannot physically agree to a ceasefire because it is not a party to the conflict," Peskov said.
In an earlier statement, Poroshenko's press office said: "As a result of the conversation (between the Ukrainian president and Putin) agreement was reached on a permanent ceasefire in the Donbass.
"Mutual understanding was achieved concerning the steps which will enable the establishment of peace," it added.
There was no immediate sign on the ground of a halt in the fighting between Kiev's forces and separatists in the mainly Russian-speaking region, which is home to much of Ukraine's heavy industry.
Earlier, Putin's spokesman was quoted in Moscow by Interfax news agency as saying the Russian leader and Poroshenko had largely agreed in their telephone conversation on what needed to be done to resolve Ukraine's six-month-old crisis.
Initial reaction from Ukrainian forces was cautious.
"At the moment that journalists told me of a cease-fire, we came under fire twice," Serhiy Melnichuk, commander of the Aidar volunteer militia battalion in the Donbass, told Ukraine's 112 TV channel.
"We have received no orders yet. Russia needs to remove its forces from our territory ... We have to stop this slaughter, we are destroying the nation."
Interfax quoted a leading separatist in Donetsk, the biggest city of the Donbass, as saying the separatists were ready to halt their military operations if Kiev also accepted a ceasefire.
"If the Ukrainian side observes its promises on a ceasefire, we are ready for a political resolution of the process," said Miroslav Rudenko, a deputy in the local assembly of the self-proclaimed Donetsk people's republic.
According to the United Nations, the war has killed more than 2,600 people and driven nearly a million from their homes in eastern Ukraine.
