Russian President Vladimir Putin said he and European Union states had tried unsuccessfully to persuade Kiev to extend a ceasefire in east Ukraine.
He also claimed the Ukrainian president had veered off the road to peace.
President Petro Poroshenko renewed a military campaign against pro-Russian rebels this morning, saying they had not abided by the ceasefire terms.
Ukrainian government forces launched air strikes and artillery assaults after Mr Poroshenko said they would "free our lands", hours after the ceasefire to allow for peace talks had expired.
"After the President's speech, the ATO (Anti-Terrorist Operation) went into action", military spokesman Oleksiy Dmytrashkovsky was reported as saying by Interfax news agency.
"We opened artillery fire, carried out air strikes at the strategic points of the terrorists and places where they are concentrated," he added.
He said rebels had fired on an SU-25 attack aircraft, damaging it, but the plane had managed to land safely at its air base.
Mr Dmytrashkovsky also denied a rebel report that a military helicopter had been brought down.
One Ukrainian serviceman had been killed and 17 wounded in the past 24 hours in rebel attacks on Ukrainian posts, he said.
The defence ministry confirmed that Ukrainian forces had launched attacks on the rebels "from the air and land".
"The terrorists' plan to significantly escalate armed confrontation has been disrupted and the threat of losses to the civilian population and service personnel has been liquidated," the ministry said on its website.
Mr Poroshenko, who accuses Russia of fanning violence in eastern Ukraine, dismissed Moscow's offers to defuse the crisis, and accused the rebels of failing to keep to the truce or follow a peace plan he had outlined.
Earlier, the speaker of Russia's lower house of parliament called for a new ceasefire in east Ukraine, Interfax news agency reported.
"We think that without a truce, without the start of dialogue, it is simply impossible to restore peace, justice and law and order in Ukraine," Sergei Naryshkin said.
Russia could face further sanctions
Russia could face more penalties from the European Union on top of existing asset freezes and visa bans unless pro-Russian rebels act to wind down the crisis in the Donetsk and Luhansk provinces.
EU leaders said on Friday they were ready to meet again at any time to adopt more sanctions on Russia.
Diplomats said they could target new people and companies with asset freezes as early as next week. More than 60 names are already on the list.
Before this morning's announcement, Mr Poroshenko met security chiefs, some of whom had called against a ceasefire extension because of military losses and fears that the rebels were using it as an opportunity to regroup and rearm.
A statement tweeted by the Foreign Ministry said 27 Ukrainian servicemen had been killed and 69 wounded since the ceasefire began on 20 June.
Mr Putin had urged during the telephone call for an extended ceasefire, a Kremlin statement said.
At Mr Putin's request, the Russian parliament last week revoked the right it had granted him in March to invade Ukraine in defence of its Russian-speakers.
Russian Foreign Minister Sergei Lavrov told state TV that Moscow was ready to allow OSCE security and rights watchdog monitors and Ukraine's border guards to enter the Russian side of the border for joint control.
Kiev accuses Russia of letting fighters and weapons to cross the porous border into eastern Ukraine.
"The revocation of permission (by lawmakers) to send Russian troops into Ukraine was positive but symbolic," Mr Poroshenko said.
"We also did not expect any concrete steps on the de-escalation of the situation, including boosting control over the border."
Poroshenko faces local anger over military deaths
Mr Poroshenko, who had been under Western pressure to extend the ceasefire, faced rising anger at home over the military deaths.
Local media said hundreds of people had gathered outside of his administration building in Kiev in anticipation of a statement on the fate of the truce.
In eastern Ukraine's flashpoint city of Slaviansk, a rebel stronghold since separatists took over the city in April,shelling could be heard, though it was unclear from which direction it was coming from.
Mr Poroshenko said he was willing to return to a ceasefire "at any moment" if it became clear that all sides were ready to carry out all aspects of the peace plan, including the freeing of hostages and creating effective border controls.