The Taliban have allegedly taken a woman from her home by force after she participated in protests in the Afghan capital, Kabul.
Mursal Ayar was arrested in the city on Wednesday, a source told the BBC, after she took part in rallies demanding equal rights for women.
Women have been participating in a string of protests which have attracted international attention.
Ms Ayar is believed to be the sixth protester to vanish in recent weeks.
The Taliban have, however, denied detaining the women. A spokesman said they were looking into Ms Ayar’s case.
“This is a case which has just happened. We are investigating it,” Taliban spokesman Bilal Karimi told the BBC.
Ayar, there are fears for Parwana Ibrahimkhail, Tamana Paryani and Ms Paryani’s three sisters Zarmina, Shafiqa and Karima who went missing on 19 January.
Ms Ibrahimkhail and Ms Paryani were part of a huge protest on 16 January, calling for women to be given work, study and political rights under the country’s new Taliban rulers.
Days later, Ms Paryani later posted a video on social media showing armed men entering her apartment block.
“Help, the Taliban have come to my house,” she said before the video ended.
In a previous interview with the BBC, Suhail Shaheen, who hopes to become the Taliban’s ambassador to the United Nations, accused Ms Paryani of “making fake scenes and shooting films in order to seek asylum abroad”.
Ms Ibrahim’s brother-in-law was also abducted while the pair were travelling in Kabul, the UN has said.
The UN’s human rights office on Saturday said again that it was “very alarmed” over the continued disappearance of people connected with the recent women’s rights protests.
“We are gravely concerned for their well-being and safety,” said Ravina Shamdasani, spokesperson for the High Commissioner for Human Rights on Tuesday.
“The lack of clear information on the location and well-being of these and other individuals, perpetuates a climate of fear and uncertainty,” she added.
The UN noted that the Taliban had on Saturday announced an investigation into the women’s disappearance but said confirmed information was still lacking.