China is holding at least five women's rights activists in detention after they planned a demonstration ahead of International Women's Day, which falls on Sunday, rights lawyers said.

Rights groups say China's government is taking an increasingly tough line against freedom of expression. The detentions have also coincided with China's annual parliamentary session.

Attorneys for two of the detained activists told Reuters the five women, who are from three cities, were taken into custody by police on March 6. They had been organizing demonstrations in several cities over the weekend against sexual harassment on public buses.

One of the women detained, Li Tingting, known by her pseudonym Li Maizi, is best known for organizing a campaign for gender-neutral toilets. Another activist, Zheng Churan, was detained in the southern city of Guangzhou. Both are in their early 20s.