“Like millions of people in Ukraine I spent hours in a shelter this morning because of the ongoing wave of attacks on Ukraine by the Russian Armed Forces,” Matthias Schmale said in a statement issued on Monday.
He added that civilians were reportedly killed and injured, while civilian infrastructure sustained heavy damage.
Separately, the UN Children’s Fund (UNICEF) in Ukraine wrote on the social media platform X that boys and girls “woke up today to sounds of air alarms and explosions”.
The office also shared photos of children and families sheltering at metro stations in the capital, Kyiv.
The attacks came in the wake of Ukraine’s recent incursion into the Kursk region in Russia and were among the most intense in weeks, according to media reports.
At least five people were killed in the strikes, which mainly targeted critical energy infrastructure, resulting in power outages and disruption to water supply.
Earlier this year, the UN and partners reported that Russia had stepped up attacks on Ukraine’s energy grid, with the UN human rights office, OHCHR, recording 50 incidents in April alone.
Mr. Schmale concluded his statement by saying it was “unacceptable” that Ukrainian citizens were having to seek safety in metro stations and other shelters instead of getting on with their lives.
“Even in war there are rules,” he said. “International humanitarian law must be respected. Civilians must be protected.”
The Representative for the UN reproductive and sexual health agency, UNFPA, in Ukraine also deplored the aerial assault in a post on X.
Massimo Diana said the attacks “tragically claimed lives” in the city of Lutsk and in the Zhytomyr region.
“We condemn these deadly assaults on critical infrastructure and call for urgent action to protect civilians,” he said.