Five Chinese feminist activists are still in police custody after authorities detained at least 10 women’s rights proponents across the country in the runup to International Women’s Day, according to a Chinese activist.

Activist Feng Yuan said those still in detention were Li Tingting, Wei Tingting, Wang Man, Zheng Churan and Wu Rongrong, the founder and executive director of the Hangzhou-based rights group Women Center. Feng said their lawyers have not been able to reach them since they were detained on Friday and Saturday.

Feng said the women had planned to observe International Women’s Day by putting up leaflets about sexual harassment in Beijing, Hangzhou and Guangzhou. Lu Jun, a board member of Women Center, said the activists ha d observed previous International Women’s Days in similar ways but without interference.

Public security has been heightened around Beijing this past week as the country’s legislature, the National People’s Congress, holds its closely watched annual session. On Saturday, the meetings included a news conference on gender equality and women’s rights issues in China. The nearly two-week long congress ends on Sunday.

Police in Beijing and Guangzhou did not respond to requests for comment.

“We’re worried that they’re still detained,” Feng said from New York, where she was participating in UN women’s issues events. “We don’t understand how this has to do with public safety. And this goes against what the Communist party and the government says they want to do to build a safer, crime-free society.”

Feng said supporters in the US have taken up the detained Chinese activists’ cause, with banners calling for their release seen during a march in New York on Sunday for International Women’s Day.