Police have picked up five individuals - four Malaysians and an Indonesian - believed to be involved in alleged terrorist activities, following a clampdown by the police in Selangor and Johor between Oct 9 and 13, said inspector-general of police Khalid Abu Bakar.

Khalid said three of them, including the Indonesian, are believed to be followers of the notorious Islamic State.

"The first suspect, aged 22 - a local - was arrested in Johor. He works as a canteen supervisor at the Health Ministry in Petaling Jaya. The Indonesian is an assistant worker at the same place. Both of them were previously arrested for Immigration-related offences.

"The third suspect is a 40 year old from Petaling Jaya, who was a senior officer with Felda Global Ventures Bhd. In August he participated in a voluntary separation scheme. He left for Turkey for Syria on Oct 21.

“But he was arrested by the Turkish authorities on Oct 25 and repatriated to Malaysia. He is believed to have joined IS," he said in a statement today.

Khalid said two others, aged 28 and 30, were picked up in Selangor and said to be part of the 'Imam Mahdi' terrorist group.

The 30 year old, who sells soyabean milk, was previously a part of the Al Ghuruba cell, which is part of the Jemaah Islamiah group. He had been arrested in Pakistan in 2003.

The 28 year old is said to have planned attacks at several locations in the Klang Valley.

All five suspects, Khalid said, are being held under the Security Offences (Special Measures) Act 2012.