A known Malaysian IS fighter in Syria, Muhammad Wanndy Muhammad Jedi, had said in a posting on his Facebook page that the group had carried out the June 28 attack on a bar in the Puchong neighborhood that wounded eight people.
If the claim was genuine it would have been the first attack by IS on Malaysian soil.
Eight injured in Malaysia hand grenade attack: police
Inspector-General of Police Khalid Abu Bakar said in a statement the two men who carried out the attack had been caught in the northeastern state of Kelantan, where they had been awaiting instructions from Wanndy to carry out further attacks.
"Following on from their arrest, police managed to seize a grenade, and it was suspected it would have been used in a planned attack," Khalid said.
He said two other people had been arrested for helping to hide the suspects.
Police had also tracked down a suspected IS member, whose cell had received orders from Wanndy, and had threatened attacks on the police headquarters in Kuala Lumpur and on government buildings in the country's administrative capital of Putrajaya, Khalid said.
Others arrested included a 17-year-old in the eastern state of Sabah, on the island of Borneo, who was believed to have been planning a 'lone wolf' attack on non-Muslims after communicating with another Malaysian IS member in Syria.
Meanwhile, three foreigners, who were ex-military, were arrested in Kuala Lumpur for allegedly using the country as a transit point to secure fake travel documents and plan an attack on a Middle East nation, Khalid said.
Islamic State linked to recent Malaysia grenade attack: police
Authorities in Muslim-majority Malaysia have been on high alert since IS-linked militants carried out an armed attack in the capital of neighboring Indonesia in January.
Police said last week 230 people, including 200 Malaysians, have been arrested since 2013 for involvement in militant activities.
In June, IS released a video of its fighters from Southeast Asia calling on its supporters to unify under one umbrella group and launch attacks in the region.
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