Indonesia's provincial broadcasting regulatory body said it will ask Batam-based Radio HangFM station for a clarification, after two Singaporeans detained under the Internal Security Act became radicalised after listening to its broadcasts.

Mr Suyono, deputy chief of broadcasting content at Indonesia's Broadcasting Commission in Riau Islands province, told The Sunday Times yesterday that it will also evaluate the station's content.

"We will meet their representative to get an official clarification and hold a dialogue, as soon as possible," he added.

Mr Suyono, who goes by one name, said the commission had sent a warning to the station last year for airing "differences in opinion about Islamic practice" which it considered "too firm in its delivery".

"Differing opinions means like the way one should pray. So, it's not to the extent of promoting terrorism and radicalism. Since the warning, we noticed they have changed and toned down their rhetoric," he said, adding that he noticed the station had recently been airing speeches rejecting terrorism.

Singapore's Ministry of Home Affairs (MHA) said last Friday it had detained two self-radicalised Singaporeans who were planning to join the Islamic State in Iraq and Syria terror group and issued Restriction Orders against two others.

Detainees Rosli Hamzah, 50, and Mohamed Omar Mahadi, 33, began listening to Radio HangFM in 2009 and 2010 respectively, MHA said.

Yesterday, an MHA spokesman said Radio HangFM "is a religious station which sometimes features speakers who preach extreme views", adding the Singapore authorities are "looking into all options" on whether to block the station.

Batam religious affairs chief Zulkifli Aka said that a group of Muslims had protested in 2014 over the station's content, which they found conservative.

The station agreed not to air "propaganda", including not "calling as infidels Muslims who don't subscribe to their beliefs", according to the agreement seen by The Sunday Times.

When this newspaper tuned in to Radio HangFM yesterday, an announcer was reading out a statement that called the media reports "untrue" and a bid to "discredit" the station.

A preacher then advised Muslims to follow Prophet Muhammad's way.

Mr Zein Alatas, the station's commissioner, told The Sunday Times yesterday that the management "strongly opposes all forms of radicalism and violence like it has been conveying all this while in its speeches".

The station broadcasts sermons by up to 20 Indonesian preachers, all of which, he said, were "based on the Quran and religious scripts".

Regarding the two Singaporean detainees, Mr Zein suggested that they could have become radicalised after reading "other materials in their own private time" rather than after listening to the station's preachers.