The raids are part of security preparations ahead of the 29th Southeast Asian Games, which will held in the country from Aug 19 to Aug 31.
The majority of the detainees are migrant workers from Bangladesh, India and Pakistan, Ayob Khan Mydin Pitchay, Malaysia’s top anti-terror official, told BenarNews.
The detainees also include workers from Nepal, Indonesia, Myanmar, Oman, Yemen, Uzbekistan, Thailand, Nigeria and Sri Lanka.
The authorities are checking to see if the detainees have been listed as foreign terrorist fighters by the Interpol, Ayob said. They are also being screened against Malaysia’s counter-terrorism database.
“Terrorism is an ongoing threat and Malaysia is putting all its effort to ensure safety and security of everyone in the country,” Ayob said.
The police released 275 were afterwards, but detained 133 as suspects for violating immigration laws.
Another suspect was being held for violation of Malaysia’s Security Offenses (Special Measures) Act, the counter-terrorism official said.
Machines for forging passports and fake immigration documents for Malaysia were among the items seized during the raids, the BBC reports.
"The operation today is the first of many that we are going to conduct in conjunction with SEA Games,” Ayob said. “The main aim is to weed out the area from any threats, including terror elements.”
As many as 200 counter-terror personnel raided homes and businesses in Masjid India, a Kuala Lumpur district on Sunday.
On Monday, police broke down doors and led scores of suspects away in handcuffs for investigation and screening, according to the BBC.
Forty foreign nationals have been arrested and deported on suspicion of terror activity since 2013, Ayob told BenarNews.
Raids conducted since 2013 led to the capture of 310 Malaysians. Of them, 66 have been freed.
Malaysia's crackdown on illegal immigration since July of this year has led to the detention of 5,500 foreign nationals, mostly from Indonesia and Bangladesh.