The Russian strikes came just hours before a unilaterally proposed Ukrainian ceasefire and days before Russia itself intends to observe a ceasefire. Volodymyr Zelenskyy condemned "cynical, vile" attacks by Russia.

At least 27 people were killed and dozens more injured in Russian strikes across eastern Ukraine late on Tuesday night, just hours before a ceasefire proposed unilaterally by Kyiv came into effect at midnight Wednesday (2100 GMT).

"With mere hours ​until Ukraine's ceasefire proposal comes into force, Russia shows no signs of preparing to end hostilities," wrote Ukrainian Foreign Minister Andrii Sybiha on social media. "On the contrary, ​Moscow intensifies terror."

At least 12 people were killed and 20 injured in the southeastern city of Zaporizhzhia after a Russian attack with guided aerial bombs was followed up by Iranian-designed Shahed drones.

"A cynical strike on facilities in the city of ​Zaporizhzhia," City Council Secretary Rehina Kharchenko told the Reuters news agency. "After the hit, the enemy intentionally began attacking those locations with Shahed drones."

Further north, six people were killed and 12 injured when powerful glide bombs smashed into the frontline city of Kramatorsk, four people were killed in Dnipro and five people were killed in a strike on gas production facilities in the Poltava region.

Zelenskyy slams 'cynical, vile' attacks
President Volodymyr Zelenskyy said that the Poltava attack was "especially vile" because Russia, like in Zaporizhzhia, launched a second missile at the same target when emergency rescuers were working at the scene.

"These are absolutely cynical, senseless terrorist strikes devoid of any military sense," Zelenskyy wrote on Telegram. "Such ​Russian strikes on our cities and villages ⁠do not cease for a single day."

The attacks came after five people were killed and 39 wounded on Monday night and after Moscow declared that it would observing a ceasefire later this week on Friday and Saturday as Russia commemorates the allied victory over Nazi Germany in World War II.

The Russian Defense Ministry said it would strike back at Ukraine if it tries to disrupt the festivities on Victory Day, which Russia marks annually on May 9 – but has continued to bombard Ukrainian cities in the meantime.

"Russia could cease fire at any moment, and this would stop the war and our responses,” said Zelenskyy, rebuking Moscow for its "utter cynicism" in continuing its attacks. "Peace is needed, and real steps are needed to achieve it. Ukraine will act in kind."

Ukrainian attacks on Russia continue
Meanwhile, before its unilateral ceasefire came into effect at midnight, Ukraine also continued its attacks on targets inside Russia, aiming at oil facilities in an effort to further disrupt Moscow's war economy.

Zelenskyy said Ukrainian forces launched their own F-5 Flamingo cruise missiles at targets including military-industrial complex facilities in Cheboksary, located more than 1,500 kilometers (900 miles) away. The regional health ministry said three people were injured.

Ukrainian drones also reportedly attacked the Kirishi oil refinery in the northern Leningrad region close to St. Petersburg, sparking a blaze in the town's industrial zone.

Within of Ukraine's midnight deadline passing, authorities in Russian-occupied Crimea, which was annexed in 2014, announced that five civilians had been killed in the town of Dzhankoi in a Ukrainian drone attack which had likely been launched before the deadline.

In total, Russia's Defense Ministry claimed that its forces destroyed 289 Ukrainian drones across 18 Russian regions.