Indonesian police arrested six suspected militants in Batam island on Friday for allegedly planning to fire a rocket in an attack on Singapore's Marina Bay.

Indonesian national police spokesman Boy Rafli Amar said in a text message that the police have identified the group as "KGR @ Katibah GR" which is accused of harbouring two Uighurs.

One of the Uighurs, named Ali has been linked to Nur Rohman, the suicide bomber who tried to attack a police station in the city of Solo in Central Java on July 5.

Boy Rafli said the 30-year-old local bomber had fetched Ali from Batam to Bogor and finally left him with an Indonesian militant named Arif Hidayatullah (alias Abu Musab) in Bekasi.

The second Uighur has been identified as Doni.

Boy Rafli said Gigih Rahmat Dewa, the group leader along with an Indonesian militant, identified as Bahrun Naim, were believed to be fighting together with the Islamic State in Iraq and Syria (ISIS) militant group since early 2015.

"They have previously planned to launch a rocket from Batam to Marina Bay Singapore," he told The Straits Times.

He added that "Gigih is suspected to have received and channeled funds for radical activities from Bahrun".