An unprecedented security law will come into force in Malaysia today amid growing controversy over the prime ministership.

Key points: Law will enable authorities to search individuals, premises and vehicles without a warrant

Law will enable authorities to search individuals, premises and vehicles without a warrant PM says law is needed to prevent terrorism in Muslim-majority Malaysia

PM says law is needed to prevent terrorism in Muslim-majority Malaysia US last week moved to seize $1.3 billion in assets linked to 1MDB

Najib Razak is embroiled in a multi-million dollar embezzlement scandal involving the state investment fund 1Malaysia Development Berhad, or 1MDB, although he denies any wrongdoing.

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The new security law will enable the Malaysian leader to designate so called "security areas" where forces can be deployed and individuals, premises and vehicles can be searched without a warrant.

Prime Minister Najib said the law was needed to counter security threats, but rights groups and the UN Human Rights Office for Southeast Asia said the law would be used to silence the community.

"We are gravely concerned that … the act may encourage human rights violations," said the UN's Laurent Meillan in a statement.

Mr Meillan also expressed concern the act could lead to "unjust restrictions" on free speech and assembly, with others saying the law was draconian and aimed at silencing critics of the Government.

"We call on the Government to revise the act to bring it in line with international human rights norms and standards," he said.

On Thursday Mr Najib defended the security law, saying it was needed to prevent terrorism in Muslim-majority Malaysia.

"My Government will never apologise for placing the safety and security of the Malaysian people first," he said in a statement.

New law can counter 1MDB critics

The Malaysian Government rammed the National Security Council Act through Parliament last December, giving it powers to declare virtual martial law in areas of the country determined to be facing a security threat.

Critics of the Prime Minister say he enacted the laws as ammunition against any moves to oust him.

Authorities in several countries are investigating allegations that investment fund 1MDB, which Mr Najib founded and oversaw, was looted over several years.

Mr Najib has stifled domestic pressure by cracking down on critics within his ruling party, scuttling investigations, and arresting whistleblowers and journalists.

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But international pressure increased last week when the US Justice Department moved to seize more than $1.3 billion in assets it says were purchased with money stolen from 1MDB.

The detailed Justice Department filings included accusations that a high-ranking Malaysian government official, clearly referring to Mr Najib, conspired in the massive theft, along with his associates and family members.

US regulators issued subpoenas to Goldman Sachs for documents related to the investment giant's dealings with 1MDB, a source close to the probe said on Friday.

Mr Najib came into office in 2009 pledging an end to ruling-party corruption and authoritarianism, but reversed course following a 2013 election setback and the financial scandal.

ABC/AFP