Bahrain has temporarily freed a female activist who has accused her government of torture in detention, rights groups said Monday.

Ebtisam al-Saegh was released late Sunday pending her trial on "terrorism" charges, Amnesty International and the Bahrain Institute for Human Rights (BIRD) said.

Two other activists, Radhi al-Qatari and Mohammed al-Shakhoori, were also released until their trials on similar charges, BIRD said.

London-based Amnesty International confirmed the charges against Saegh had not been dropped.

Bahrain's justice ministry did not respond to a request for comment.

Saegh was detained in July after retweeting a series of posts critical of Bahrain's king and its security agency and charged later the same month with "terrorism".

Her detention prompted warnings from rights groups she was at risk of torture, after Saegh accused Bahraini security services of torture and sexual assault during a previous arrest in May.

In April, Bahrain's parliament approved military courts trying civilians charged with "terrorism", a vaguely defined legal term in the Sunni-ruled kingdom.

Authorities have cracked down on political dissent since a wave of protests erupted in 2011 demanding an elected government in the Shiite-majority country. 

A key US ally located between Saudi Arabia and Iran, Bahrain is home to the US Fifth Fleet and a British military base that is still under construction.

The government accuses Iran of state-sponsored "terrorism" and of training Bahrainis to overthrow their monarchy, but Tehran denies any involvement.