Four Indonesians were arrested in Singapore after clearing the Johor checkpoint, as Singaporean authorities believe they were en route to the Middle East to join militant group Islamic State (IS).

The four suspects, including a 15-year-old boy, were arrested at the Woodlands Checkpoint, Singapore's Straits Times reported.

Indonesian police believe the four are linked to radical preacher Aman Abdurrahman, who reportedly masterminded the Jan 14 attack in Jakarta from his jail cell in Nusakambangan prison.

The four were handed over to Indonesian police at Batam Island on Sunday, the daily reported.

Singaporean authorities saw the red flag when it was found they took a ferry from Batam to Singapore before heading to Johor, and then returning to Singapore three hours later, it reported.

This comes after Australia on Sunday warned its citizens that a terror attack against Kuala Lumpur may be in the works.

The Jakarta attack prompted high alert in the region, including in Kuala Lumpur where military and police now conduct joint patrols in dense public spaces and tourist attractions.

Malaysian police say they will continue with the patrols to convince residents and visitors that Kuala Lumpur is safe.