Lawyers representing Bersih chairperson Maria Chin Abdullah filed a habeas corpus application today to challenge her detention under the Security Offences (Special Measures) Act 2012 and sought her immediate release.

Lawyer Ambiga Sreenivasan said the application was filed with the condition of Maria's detention in solitary confinement as one of the grounds.

"We have also stated that Sosma was wrongly used against her. And that the whole method in which she was taken in was unlawful," Ambiga told reporters at the lobby of the High Court in Kuala Lumpur this morning.

Following Maria's arrest last Friday, Ambiga confirmed that she was being detained under Section 4(5) of Sosma, which provides for up to 28 days in detention without trial.

It has been previously pointed out that there are no grounds under any law governing detention in Malaysia to keep her in solitary confinement, and that such treatment could amount to torture.

Ambiga, who is also National Human Rights Society (Hakam) chairperson, was accompanied by other members of Maria's legal team as well as Maria's three sons.

Habeas corpus is an order to bring a jailed person before a judge or court to find out if that person should really be in jail.

Asked for comment on the release of red-shirts leader Jamal Md Yunos today after serving a four-day remand notice, Ambiga said she was not aware of the matter.

"It is (however) very clear that Maria has been singled out for this ridiculous and horrendous treatment.

"They can investigate her without subjecting her to detention under Sosma," she added.

The matter is set for case management on Thursday before judicial commissioner Nordin Hassan

Maria was arrested and detained after a police team from Bukit Aman, together with officers from the Companies Commission of Malaysia, raided the Bersih office in Petaling Jaya last Friday.

Maria is also being investigated under Section 124C of the Penal Code for engaging in activities detrimental to parliamentary democracy.

This is after it was revealed that the electoral reform movement received funds from the Open Society Foundations, which is linked to billionaire George Soros.

Jamal, who is Umno Sungai Besar division leader, was also arrested last Friday, under Section 147 of the Penal Code for alleged rioting.