Malaysian Indian lawmaker Karpal Singh received an envelope with two live bullets and a letter that threatened to "burn his entire family" if he clashed with the Malay rulers.
Singh, who heads the opposition Democratic Action Party, said he was in Kuala Lumpur when an employee at his Penang office called to inform him of the letter that was mailed to his house in George Town.
According to Star Online, Singh showed the reporters the bullets, the letter which was written in red ink, and the envelope which was postmarked "Ipoh, Perak, Feb 12".
The letter said "not to fool around with the Malay rulers and Malays in general" and threatened to burn his entire family.
Singh had said Sultan Azlan Shah, the royal constitutional head of Perak, could be taken to court for his partisan role in the change of guard in the state.
Some leaders of the rival alliance Barisan Nasional had called it an "insult" to the royalty and hence "seditious".
Penang Chief Minister Lim Guan Eng, who visited Singh at his house, urged police to provide protection to him, his family and his properties including both his offices in Kuala Lumpur and Penang.
Police confirmed that it had received Singh's complaint.