A large chunk of an apartment building in Dnipro collapsed after being hit during the overnight attack.
Four corpses were recovered from the rubble, regional governor Oleksandr Hanzha said on Saturday.
The site was struck again in a daytime attack, authorities said, while rescuers were working there.
The second attack killed one person and injured seven.
Moscow has been launching smaller barrages of dozens of drones every night at Ukraine, interspersing them with occasional large-scale attacks that use hundreds of drones and dozens of missiles.
Thick columns of black smoke could be seen streaming into the sky on Saturday morning, as local media warned residents in the city about worsening air quality.
A Reuters reporter saw a Russian drone being destroyed in the sky over the ruined apartment block as rescuers were working in the rubble.
In total, more than 30 people in the city were wounded, officials said.
"Russia is deliberately prolonging its terror against our people, continuing to target critical infrastructure and residential buildings," Prime Minister Yulia Svyrydenko said.
In the northern region of Chernihiv, missile and drone attacks killed two people and wounded seven others, the governor there said.
"Every strike like this must remind our partners that the situation needs immediate and firm action, rapid strengthening of our air defences," President Volodymyr Zelenskiy said.
Drone fragments damaged an electricity pole and household annex in NATO member Romania, which borders Ukraine, authorities there said, although there were no casualties.
Ukraine has recently stepped up its own drone attacks hitting Russian territory.
Authorities in the Russian city of Yekaterinburg said on Saturday a Ukrainian drone crashed into an apartment building there, causing minor injuries.
The Ukrainian leader was visiting Azerbaijan on Saturday to sign agreements on defence and energy co-operation.
Kyiv is seeking to strengthen its diplomatic and security alliances by leveraging wartime experience in countering vast aerial attacks, particularly its experience in downing hundreds of drones with low-cost methods.
Zelenskiy posted a picture of him meeting Azerbaijani President Ilham Aliyev, and said he also met a Ukrainian military team "which is sharing Ukraine's experience in protecting the skies".
Azerbaijan has a long border with Iran, with which it has tense relations. Azerbaijan has also fought multiple wars with its other neighbour Armenia since 1991.
Since the US and Israel attacked Iran earlier in 2026, triggering a war in the Middle East, Kyiv has worked hard to build security co-operation with Middle Eastern nations concerned about Iranian drone and missile bombardment.
Russia's overnight attack on Saturday used 619 drones and 47 missiles, Ukraine's air force said on Telegram, adding that it downed 580 drones and 30 missiles.
Russia's defence ministry said it had hit military-industrial and energy targets in Ukraine overnight.
It did not comment on the strike on the apartment block in Dnipro.
