A police station in Negeri Sembilan received an envelope marked "IS Ancaman" (IS threat), which, among others, contained the photographs of Prime Minister Najib Abdul Razak and his deputy Ahmad Zahid Hamidi, according to a news report.
China Press said the other photographs in the two-page letter addressed to the Nilai police chief included that of inspector-general of police Khalid Abu Bakar, attorney-general Mohamad Apandi Ali and Myanmar state counsellor Aung San Suu Kyi.
The letter also stated there are "316 members and four experts in Kuala Pilah", "114 members and eight experts in Nilai" and "97 members and two experts" in Port Dickson.
Though it was not mentioned if this referred to the number of IS members in Negeri Sembilan, the report however claimed the figures were included as a "show of strength" to the police.
There was also no clarification with regard to the "experts".
Meanwhile, China Press quoted Special Branch counter-terrorism division assistant director Ayub Khan Mydin Pitchay as stating that the matter is being investigated.
He said police had received a similar threat about two months ago.
Previously, an IS propaganda video featured a Malaysian, who hailed from Negeri Sembilan, warning that the terrorists would attack police personnel.
"Those of you in Bukit Aman (federal police headquarters), you will no longer have peace.
"We will slaughter you... when we return. Our friends back home will hunt you down," said Mohd Rafi Udin, who is currently believed to be in Syria.
Malaysia witnessed its first IS attack in late June when a grenade was hurled into a night club in Puchong, which left eight injured.
When met at a Hari Raya open house today, Khalid said the police had received four or five letters of such nature sent by the perpetrators.
"Yes, we take note of that. I feel that the community need not worry (about it).
"We take the threat seriously. But, as I said before, this would not weaken our morale in performing our duties.
"We do not know (the sender as) it was sent by post, but we will find them," he said.
However, the top cop was perplexed by the mention of a leader from Myanmar in the letter sent to the police.
"They also threatened a Myanmar leader. What it has got to do with Myanmar? We shall have a look," Khalid said.