Police in Vietnam’s capital Hanoi on Sunday blocked access to a piano recital held in the city’s Opera House, roughing up a group of environmental activists who had hoped to attend and preventing them from entering, sources said.

The concert, titled “Awake” and performed by pianist Pho An My, featured an environmental theme, the civil society group Green Trees said in a Facebook posting after its members were turned away.

“A large crowd of security forces had gathered outside, just as if they were preparing to disperse a protest, and scores of people were roughed up,” the environmental advocacy group said, adding that paintings about the environment were forbidden from display in the concert hall.

“Security men were stationed every five meters [15 feet] surrounding the theater, and were stopping people from live-streaming or taking pictures. Only the security people were allowed cameras, and they pointed them at concertgoers like they were monitoring criminals,” Green Trees said.

“All gates to the theater were locked right after the concert started, so nobody could leave or enter, and no one could give the artist flowers.”

In its Facebook posting, Green Trees said that police may have thought that concert organizers had received funding from “foreign sources” by way of the environmental group, which also advocates for human rights, freedom of expression, and freedom of assembly in the one-party communist state.

'They were brutal to us'

Speaking to RFA’s Vietnamese Service on Nov. 15, Green Trees member Cao Vinh Thinh said that she and her husband had arrived at the Opera House at about 7:30 p.m. on the evening of the concert.

“As soon as we stopped our motorbike next to the theater, we were approached by a group of about 10 people, two of whom I recognized because they have followed me around for years,” Thinh said, adding that the group ordered her to return home, later forcing her and her husband into a car and driving them home themselves.

“I’m very upset,” Thinh said. “We had bought two tickets, but the money doesn’t matter. What matters most is how they treated us.”

“They were brutal to us, and they deprived us of our rights as citizens. We hadn’t broken any law or rule,” she said.

Also speaking to RFA, pianist Pho An My said that she had only focused on her performance and was unaware of what was happening outside.

“I’m just an artist, and I want to express my thoughts. I’m not an environmental activist,” she said.

Calls seeking comment from police in Hanoi’s Hoan Kiem district rang unanswered on Monday.

Civil society groups restricted

Independent civil society organizations are severely restricted by Vietnam’s communist government, which also controls all media, censors the internet, and restricts basic freedoms of expression.

On Oct. 25, Vietnamese authorities detained environmental activist and filmmaker Thinh Nguyen, a member of Green Trees, in what was thought to be the government’s response to a film, “Do Not be Afraid,” about other environmental activists who were detained for their advocacy.

Green Trees had called on Vietnam’s government just two years before to let it help monitor the payment of compensation to citizens affected by a massive toxic-waste spill in 2016 that left thousands jobless in four central coastal provinces.