Malaysian military personnel and policeman stand guard outside a shopping centre in Kuala Lumpur (AP)

Strict security laws are crucial to fighting terrorism, Malaysia's leader warned as the Islamic State group vowed revenge over a crackdown on its members.

Prime Minister Najib Razak says the terrorism threat is "very real" and that the laws are vital to ensure Malaysia is not open to infiltration.

Opening a two-day counter-terrorism conference, Mr Najib said "the best way to uphold civil liberties is to ensure the safety of the nation".

Human rights activists have slammed a law implemented last year that revives detention without trial.

Another law approved last month that gives sweeping powers to a council led by the prime minister has also been criticised.

Police earlier said IS, also known as Daesh, had posted a video that warns of attacks over the arrest of its members.

PA Media