The suspects were rounded up over the weekend in various parts of the Muslim-majority country, minister Saifuddin Nasution Ismail said in a statement.
He said an initial investigation by the police "has also found that there are threats against His Majesty the (king), the prime minister, prominent figures and top leadership of the Malaysian police force".
The six men and two women were from diverse backgrounds, including unemployed and educated professionals, added the minister.
In March, a machete-wielding attacker suspected of ties to an Al-Qaeda-linked group stormed a police station in the state of Johor and killed two officers.
The attacker, who police said had links to Jemaah Islamiyah (JI), had slashed one officer before grabbing a gun and shooting another.
JI has been blamed for a series of deadly bomb attacks in the region including the 2002 bombings in the Indonesian resort island of Bali that killed 202 people, including 88 Australians.
Police inspector-general Razarudin Husain in March said that Malaysia would be scaling up security.