Inspector-general of police Khalid Abu Bakar has warned atheists against causing "unease" among Malaysians, particularly Muslims.

"I wish to advise atheists to not cause unease among Malaysians, particularly Muslims who are against those who are irreligious.

"Their activities must not cause unease. I am warning them. Don't think you can do whatever you want. Be mindful of the law," he told reporters at Bukit Aman today.

He said the Islam is the official religion of the country while atheism is not mentioned in the Federal Constitution.

He said the police will look into laws which allowed them to act appropriately against those who cause unease among Muslims.

Asked if there had been complaints by atheists over threats by Muslims, Khalid did not confirm this.

"If they receive threats, which is a violation of the law, we will investigate and take action," he said.

Last week, Rizal Mansor, the special aide of the prime minister's wife, had expressed concern over the emergence of an "atheist club" in Malaysia.

Following this, the various authorities have claimed that investigations on the purported club were already underway.