Singapore said on Friday it had boosted security measures on its borders and internally after six men suspected of planning an attack on the island were arrested by Indonesian authorities.

"MHA (Ministry of Home Affairs) is aware that plans were being made by the six terror suspects arrested by the Indonesian authorities," the ministry said in a statement on Friday.

"Our security agencies have been coordinating closely with the Indonesian authorities since the discovery of this attack plot, to monitor the activities of the group and to apprehend those involved."

Rocket attack

The six suspected Indonesian militants were arrested on Batam island, just to the south of Singapore, on Friday.

An Indonesian police spokesman, Agus Rianto, told reporters that the men were believed to be planning attacks on vital infrastructure including police offices.

"We also obtained information that these suspects, with one ISIS terrorist in Syria now, planned to attack Singapore via Batam," he said, using an alternative name for the extremist "Islamic State" (IS) group.

A spokesman for Indonesia's National Police, Maj. Gen. Boy Rafli Amar, said the militants were planning to launch a rocket attack on Singapore's busy Marina Bay.

IS links

The men are suspected to have links with Bahrun Naim, an Indonesian who is fighting for IS in Syria. Naim is thought to have been involved in the planning for an attack in the Indonesian capital, Jakarta, in January, in which eight people were killed, including the four attackers.

Amar said all the men claimed membership in Katibah Gigih Rahmat, a little-known extremist group.

Singapore has never experienced any attack by Islamist extremists, and is seen as being one of the safest countries in the world.

tj/rc (Reuters, AP)