"In general, as of Easter morning, we can say that the Russian army is trying to create a general impression of a ceasefire, but in some places it does not abandon individual attempts to advance and inflict losses on Ukraine," Zelenskiy said in a post on social media.
Putin announced the surprise one-day ceasefire before heading to an Orthodox Easter service late on Saturday, ordering his forces to "stop all military activity" along the front line in the three-year-old war.
The gesture followed a US announcement that it could abandon peace talks within days unless Moscow and Kyiv showed they were serious about negotiating.
Fighting was to stop from 6 pm Moscow time on Saturday until midnight on Sunday night, Putin said.
But Zelenskiy said there had been hundreds of instances of shelling on Saturday evening. Early on Sunday, Ukrainian forces reported 59 instances of shelling and five assault attempts along the front line, he said.
"Russia must fully comply with the conditions of silence," Zelenskiy said.
He reiterated that Kyiv was willing to extend the ceasefire for 30 days but said that if Russia kept fighting on Sunday, so would Ukraine.
"Ukraine will continue to act in a mirror manner," he said.
Putin's unilateral move, to extend over 30 hours, came after US President Donald Trump said negotiations between Ukraine and Russia are "coming to a head" in his push to end the grinding three-year war.
"Based on humanitarian considerations ... the Russian side announces an Easter truce. I order a stop to all military activities for this period," Putin told Valery Gerasimov, chief of Russia's general staff, at a televised meeting.
"We assume that Ukraine will follow our example. At the same time, our troops should be prepared to repel possible violations of the truce and provocations by the enemy, any aggressive actions."
The ceasefire was set to cover Easter Sunday, the height of the Christian calendar, which falls on Sunday this year for all Orthodox, Catholic and Protestant Christians.
The Ukraine president dismissed the proposal as "yet another attempt by Putin to play with human lives".
In a post on social media platform X, Zelenskiy quoted Ukraine's top commander as saying that Russian assault operations "continue on several frontline sectors, and Russian artillery fire has not subsided".
"Therefore, there is no trust in words coming from Moscow."
The governor of Kherson province Oleksandr Prokudin in southern Ukraine said Russian air strikes began shortly before the truce was due to start and continued after.
He posted a picture of a damaged building.
"Unfortunately, we are not seeing any sort of calm here. The shelling continues and our civilians are under fire," he wrote on Telegram.
Reuters could not independently verify the situation at the front.
Ukrainian bloggers who cover the war said firing continued along the entire line of contact but public broadcaster Suspilne quoted servicemen on the eastern front as saying the number of Russian attacks had declined.
The Russian defence ministry said its troops had been instructed about the ceasefire and would adhere to it, provided it was "mutually respected" by Ukraine.
Putin has proclaimed unilateral pauses in fighting in the past with little effect on the battlefield, including a 36-hour proposed truce for Orthodox Christmas in January, 2023, which Ukraine rejected.
Russia and Ukraine both confirmed a swap of more than 500 prisoners of war on Saturday, mediated by the United Arab Emirates.
Zelenskiy, in a post on Telegram, said 277 Ukrainian service personnel had returned home from Russian captivity.
Russia's Defence Ministry said 246 servicemen had been handed over by Ukraine.
It said a further 31 injured prisoners of war had been handed over to Ukraine and 15 of its own wounded servicemen had also been returned by Ukraine.
All Russian servicemen were now in Belarus, awaiting transfer back home.
Video footage posted by Dmytro Lubinets, Ukraine's parliament commissioner for human rights, showed a gathering of Ukrainian servicemen, many wrapped in the blue and yellow flag of Ukraine in a wooded area alongside several buses.
The men were then seen seated on the edge of a tarmac shouting patriotic slogans.
with AP and DPA
