Mariupol, Ukraine - The United Nations and aid organizations have condemned Russia's attack on a maternity hospital in the Ukrainian city of Mariupol.

UN Secretary-General António Guterres called the attack "horrific" in a tweet.

"Civilians are paying the highest price for a war that has nothing to do with them. This senseless violence must stop. End the bloodshed now," he asserted.

Doctors Without Borders (MSF) said it could not confirm "this was a targeted attack" but that its staff said "houses and hospitals have been damaged during the fighting over the past days."

Ukraine conflict Zelensky makes rare disclosure of meeting with CIA director in Ukraine

"With active shelling, gunfights, and aerial bombardment in Mariupol ongoing, seeking health care has become increasingly hard, especially for expecting mothers and elderly people who are limited in their movements," MSF emergency manager Kate White said in a statement.

"I am horrified by the reported attack today on a maternity hospital in Mariupol, Ukraine – an attack which reportedly left young children and women in labor buried beneath the rubble of destroyed buildings," said UNICEF executive director Catherine Russell. "We do not yet know the number of casualties but fear the worst."

Ukrainian President Volodymyr Zelensky called it "proof of a genocide" against his people.

17 pregnant women and employees were injured in the bombing, according to the head of the Donetsk Oblast military administration, Pavlo Kyrylenko. The Associated Press cited Mariupol city officials, who said at least three people had been killed in the strike.

Meanwhile, Russian Foreign Minister Sergei Lavrov on Thursday dismissed all accusations. After a meeting with his Ukrainian counterpart, Dmytro Kuleba, at a Turkish resort in Antalya on Thursday, he spoke of "manipulation" of the entire world with information on alleged atrocities by the Russian army.

Offering no proof, Lavrov claimed the Mariupol hospital was being used by the ultra-right fighters of the Ukrainian battalion Azov.