The unilateral ceasefire announced by Kiev was due to take effect on Wednesday, but Ukraine accused Russia of new strikes just hours after attacks killed at least 28 people in cities across the war-battered nation.
Russian authorities did not immediately report any Ukrainian strikes several hours into the proposed truce, while officials in Ukraine's southern Zaporizhzhia region said early on Wednesday that Moscow fired on their infrastructure.
Moscow and Kiev each announced unilateral ceasefires over different dates this week, with Russia demanding a pause to coincide with its annual World War II Victory Day commemorations on May 9.
Ukrainian President Volodymyr Zelenskyy accused Moscow of "utter cynicism" for launching deadly strikes while seeking a halt to hostilities.
Ukraine's Interior Minister Igor Klymenko said late on Tuesday, before Kiev's halt was due to take effect, that authorities were dealing with the aftermath of Russian strikes in regions including Poltava, Kharkiv, Donetsk, Dnipropetrovsk, Zaporizhzhia, Kherson, Odessa, Chernigiv and Sumy.
"As of now, 27 people have been killed and at least 120 injured as a result of today's Russian strikes across the country," Klymenko said.
A subsequent update from the eastern city of Kramatorsk added one more fatality.
Ukrainian drone strikes also killed five civilians, according to an early Wednesday update from the head of the Crimea region, which Russia annexed in 2014 from Ukraine.
Russia attacked the city of Dnipro late on Tuesday, nearing Kiev's deadline.
"With mere hours until Ukraine's ceasefire proposal comes into force, Russia shows no signs of preparing to end hostilities. On the contrary, Moscow intensifies terror," Ukraine's Foreign Minister Andrii Sybiga said on X.
Zelenskyy earlier described an attack that killed 12 people in Zaporizhzhia, Ukraine's southern city close to the front line, as having "absolutely no military justification".
Russian strikes also hit the centre of Kramatorsk, the last hub under Kiev's control in the embattled Donetsk region.
Six people were killed, according to an update by Kramatorsk city's military administration, Oleksandr Goncharenko, late on Tuesday, revising initial reports of five dead.
Zelenskyy said that the attack on Kramatorsk "hit right in the city centre, targeting civilians".
Four civilians were killed in Dnipro, he said.
The attacks were the deadliest in weeks, and peace efforts have gone quiet.
Yet, US Secretary of State Marco Rubio spoke by telephone on Tuesday with Russian Foreign Minister Sergey Lavrov, according to the State Department.
The two, who spoke at Lavrov's request, "discussed the US-Russia relationship, the Russia-Ukraine war, and Iran," State Department spokesperson Tommy Pigott said, without giving details.
Russia confirmed the call and noted they discussed the "schedule of bilateral contacts", but did not elaborate.
