CAIRO (Reuters) - Egyptian police on Friday detained an activist after she posted a video on social media criticizing the government for failing to protect women against sexual harassment and over worsening living conditions, Amnesty International said.

The rights group said the arrest of Amal Fathy, a member of the now banned April 6 youth movement which played a role in 2011 mass protests that forced President Hosni Mubarak out of office, was a “new low in Egypt’s crackdown on freedom of expression”.

Egyptian police could not immediately be reached for comment, but a security source said Fathy had been detained over a complaint that she had insulted the Egyptian state through an offensive social media posting.

Human rights groups have repeatedly criticized Egypt’s human rights situation, saying conditions in the country have continued to deteriorate under President Abdel Fattah al-Sisi, who came to power in 2013 after the army overthrew Islamist President Mohamed Morsi following protests against his rule.

Amnesty International said that in the video posted on Facebook May 9, Fathy spoke about the prevalence of sexual harassment in Egypt, criticized the government’s failure to protect women and for deteriorating human rights, socioeconomic conditions and public services.

“It is a dark day when the Egyptian authorities are more concerned with silencing a woman who speaks out about sexual harassment than taking steps to address the issue,” said Najia Bounaim, North Africa Campaigns Director at Amnesty International.

Sisi’s supporters say his tough security and economic measures are needed to keep the country stable as it recovers from political chaos and tackles grave economic challenges and the Islamist insurgency.

Amnesty said Fathy was detained from her home at 2:30 A.M. on Friday, together with her husband, Mohamed Lotfy -- a human rights lawyer, and were taken to a police station in Maadi in southern Cairo.

Lotfy was freed some three hours later but Fathy was kept in custody to allow a prosecutor to examine her case.

A prosecutor later ordered her detained for 15 days for questioning on charges of incitement to overthrow the ruling system, publishing lies and misusing social media, according to a lawyer at the Egyptian Commission for Rights and Freedoms, where her husband works.

Egyptian media had earlier slammed Fathy, saying she had used foul language in the 12-minute recording in which she seemed to express her anger at poor public services at a local bank, over heavy traffic, sexual harassment by a local taxi driver and over a general deterioration in living conditions.

An Egyptian security source said: “She is accused and wanted for arrest in relation to complaints accusing her of insulting the Egyptian state, by publishing a posting that contained swearing and defamation against Egypt.”