Suspected Isis militants
Some of the 12 suspects linked to the Isis militant group being lined up by police anti-terrorism unit.Royal Malaysia Police

Malaysian police have arrested 12 people on Sunday (26 April), just one day before the country hosts a Southeast Asian summit, for planning a terrorist attack by Islamic State.

National police chief Khalid Abu Bakar said the suspects were arrested in a western suburb of the capital Kuala Lumpur.

"The suspects are believed to be planning to cause civil unrest in the country," Khalid said on the official Malaysia police Facebook page.

Bakar said the suspects were all Malaysian men, ranging in age from 17-41 and suspected of being supporters of Islamic State (Isis).

Police also seized 20kg of ammonium nitrate, potassium nitrate, two litres of kerosene and remote-control devices, Bakar said in a statement.

"They had planned to launch attacks in Malaysia on April 25 and April 26," Khalid said, targeting "strategic" locations in and around Kuala Lumpur.

ASEAN summit

The capital city is hosting a summit on Monday of the 10-member Association of Southeast Asian Nations. During the meeting, Malaysia was calling on other Southeast Asian countries to unite against anti-terrorism.

During 2015, the country announced a series of arrests that authorities say have involved suspected supporters of IS.

Police say that dozens of citizens have travelled to Syria to join the Islamic jihad, and also warned of radicalised returnees staging attacks in Malaysia.

On April 17, IS-inspired militants were arrested, plotting to kidnap high-profile figures, rob banks and carry out terror attacks, according to police.

In that month, the government passed an anti-terrorism law that allowed police to hold suspects almost indefinitely without judicial review.

The move has been attacked by parliamentary opposition and human rights groups, who condemn the use of the government using security laws against political opponents.

The recent emergence of an IS recruitment video featuring young Malay boy attending religious classes and engaging in weapons training in IS-held territory caused an outcry in Malaysia. Estimates of the number of Malaysian fighters in Isis vary from between 60 to almost 150.

Estimates of the number of Malaysian fighters in Isis vary from between 60 to almost 150.