The parents of five Chinese feminists detained for more than a month have issued an eleventh-hour plea to authorities for their release, as a lawyer for the activists said prosecutors have until Monday to charge them.

The young women face being charged with "picking quarrels and provoking trouble", which could see them jailed for up to five years after they were detained by police in early March.

The vague charge of "provoking trouble" has been increasingly used by Chinese police under President Xi Jinping to detain and jail protestors for holding small-scale demonstrations.

The five women -- Li Tingting, 25, Wei Tingting, 26, Wang Man, 32, Zheng Churan, 25, and Wu Rongrong, 30 -- had in recent years been linked to several stunts aiming to highlight issues such as domestic violence and the poor provision of women's toilets.

They were taken into custody a day ahead of International Women's Day on March 8 as they were preparing to hand out leaflets about sexual harassment.

The activists are "young, kind-hearted, and full of a sense of responsibility to society," ten of their parents and spouses wrote in a letter to Beijing prosecutors that was posted online Saturday.

"These five girls, who we care for and love deeply, have not made a mistake, let alone committed a crime," they added.

Their detention has prompted renewed condemnation of China's tight controls on political activists from human rights groups as well as the US.

Police interrogations of the women -- several of whom suffer from chronic health problems such as asthma and an unspecified heart condition -- have focused on a 2012 stunt named "Occupy Men's Rooms", one of their lawyers, Liang Xiaojun, told AFP on Sunday.

Prosecutors have until Monday to formally approve their arrest, or police will be obliged to release the women, he added.

The parents said in their letter that the women "have been detained for over a month and we have not had a decent explanation".

"Please restore their freedom and dignity as soon as possible!," they added.