Alexei Alexandrov/AP
A Chinese opera singer sparked a diplomatic row after she was filmed singing the Soviet war song "Katyusha" inside the Mariupol Drama Theater.
CNN  — 

Chinese opera singer Wang Fan has sparked a diplomatic row after she was filmed singing the Soviet war song “Katyusha” inside the Mariupol Drama Theater in Ukraine where hundreds were killed last year.

Wang was part of a group of Chinese bloggers visiting the occupied Ukrainian city.

“Katyusha” is a Soviet-era folk song that gained popularity during World War II, calling on the population to serve and defend their land.

The Ukrainian Ministry of Foreign Affairs accused the group of violating its state borders.

“The performance of the song “Katyusha” by Chinese ‘opera singer’ Wang Fan on the ruins of the Mariupol Drama Theater, where the Russian army killed more than 600 innocent people, is an example of complete moral degradation,” spokesman for the Ukrainian Ministry of Foreign Affairs Oleg Nikolenko said in a Facebook statement Friday.

“Their arrival is illegal. It grossly violates Ukrainian legislation regulating the crossing of the state border by foreigners,” Nikolenko said.

“Ukraine respects the territorial integrity of China and expects the Chinese side to explain the purpose of the Chinese citizens’ stay in Mariupol, as well as the way they entered the temporarily occupied Ukrainian city.”

The Ukrainian Mayor of Mariupol Vadym Boichenko echoed criticism of the visit.

China is yet to comment on the incident and neither has Wang.

In a statement issued on Chinese social media platform Weibo, Wang’s husband applauded his wife’s “strength, bravery and determination.”

“The ex-Ukrainian residents, Russian soldiers and civilians who settled here have been working hard to resist various attacks by NATO mercenaries and the Ukrainian army,” he wrote.

“Therefore, when local Russian-Ukrainian residents heard the song, they expressed that they were deeply inspired and would continue to fight and fight for peace and the right of survival.”

Mariupol’s Drama Theater was bombed on March 16, 2022, while hundreds of people were sheltering inside.

Mariupol City Council, who shared an image of the destroyed building, said Russian forces had “purposefully and cynically destroyed the Drama Theater in the heart of Mariupol.”

Satellite images showed that the word “children” was spelled out on two sides of the theater before it was bombed.