China's parliament has approved a revised criminal procedure law that aims to restrict police powers to secretly detain criminal suspects.

The law, passed Wednesday on the final session of the 10-day National People's Congress, codifies the already common practice of “disappearing” suspects into informal detention centers, where many have reported being tortured.

Lawmakers scrapped an earlier controversial proposal that would have legalized such secret detentions for criminal suspects. But the new law still effectively allows police to secretly hold for up to six months anyone accused of terrorism or endangering national security – charges often used to detain government critics.

Some rights groups cautiously welcomed certain provisions of the new law, including a clause that requires police to notify relatives of those held at unofficial locations within 24 hours of being detained.

Critics say the law is not likely to improve human rights, and that police may simply continue to ignore laws protecting against detainee abuse. But NPC Chairman Wu Bangguo said the government will make sure that police are aware of the new law.

“We'll make the publicity for the revised criminal law, and get it widely acknowledged and make good preparations for the law enforcement. We'll make sure the law is faithfully carried out, punish the criminals, protect human rights and maintain stability.”

He said the law will be strictly enforced.

Human Rights Watch said certain aspects of the law – if implemented – could protect the rights of ordinary criminal suspects. Specifically, it mentioned stricter time limits for detentions, better guarantees for access to a lawyer and greater protection for juvenile and mentally ill suspects.

China's official Xinhua news agency said the law also outlaws the collection of evidence obtained as a result of torture.

Forced disappearances are commonly used to silence dissidents in China. Instances of such detentions have increased dramatically in recent months, as Beijing has sought to prevent popular uprisings like those that spread through parts of the Middle East and North Africa in 2011.