Both Kyiv and Moscow had accused each other of thousands of attacks that violated the truce that the Kremlin indicated on Sunday would not be extended.
Washington said it would welcome an extension of the truce, and President Volodymyr Zelenskiy reiterated several times Ukraine's willingness to pause strikes for 30 days in the war.
But Putin, who launched Russia's invasion of Ukraine in February 2022 and who ordered on Saturday the halt in all military activity along the front line until midnight Moscow time on Sunday, did not give orders to extend it.
"There were no other commands," Russia's TASS state news agency cited Kremlin's spokesman Dmitry Peskov as saying when asked whether the ceasefire could be prolonged.
Some regions in eastern Ukraine were under air raid alerts starting minutes after midnight on Monday, according to data from the Ukrainian air force, with the alerts gradually extending towards the central regions of the country.
"We urge city residents to immediately go to the nearest shelters and remain there until the alert is over," Kyiv's military administration said in a social media post at 4.41am local time.
Blasts shook the Ukrainian port city of Mykolaiv early on Monday, Mayor Oleksandr Senkevich said on Telegram. But he did not say whether it was air defence systems in operation or whether the Russian air weapons hit a target.
While there were no air raid alerts in Ukraine on Sunday, Ukrainian forces reported nearly 3000 violations of Russia's own ceasefire with the heaviest attacks and shelling seen along the Pokrovsk part of the frontline, Zelenskiy said earlier on Monday.
Russia's Voronezh region that borders Ukraine was also under air raid alerts for two hours overnight, the region's governor said on Telegram.
Russia's defence ministry said on Sunday that Ukrainian forces had shot at Russian positions 444 times and said it had counted more than 900 Ukrainian drone attacks, saying also that there were deaths and injuries among the civilian population.
Reuters could not independently verify the battlefield reports.
US President Donald Trump, hoping to clinch a lasting peace deal, struck an optimistic note on Sunday, saying that "hopefully" the two sides would make a deal "this week" to end the conflict.
On Friday, Trump and US Secretary of State Marco Rubio said the US would walk away from peace efforts unless there are clear signs of progress soon.
