The counter-terrorism unit in Indonesia questioned eight nationals who were deported from Malaysia after being caught possessing Islamic State (Isis)-linked images. They were being held at the headquarters of the Riau Islands police's mobile brigade on Batam Island.

The arrested Indonesians, aged between 16 and 37, are reportedly students in West Sumatra. They were stopped by Singapore's Immigration Checkpoint Authority at the Woodlands Checkpoint in the early hours of Wednesday (11 January) as they were trying to enter Singapore.

Riau Islands Police chief Inspector General Sambudi Gusdian said Singapore authorities found three pictures of IS (Daesh) flag, an Isis activity and a "sandal bomb structure" in the mobile phone of the oldest member of the group.

"Singapore refused their entrance and put a 'Not To Land' stamp into their passports based on the mobile phone examination," The Straits Times quoted Sambudi as saying.

The Asian Correspondent quoted a source telling Malaysian news agency Bernama that Singaporean authorities "placed the suspects under the 'No Time Limit' prohibited entry status into the republic before handing them over to Malaysian police for further investigation" after they found Isis content in one of the mobile phones.

"After the investigations, the suspects were deported to Batam, Indonesia, by ferry before being detained by Indonesian National Police (INP) and Riau Police two hours later for follow-up investigations," the source said.

Preliminary investigations reportedly revealed that the students had been in Malaysia since 3 January, with one of them seeking medical treatment in the country. The investigation also revealed that the group went to Perlis, Malaysia, and later travelled to Pattani, Thailand, on an excursion to learn about the education system in the province.

The suspects then returned to Malaysia on Monday (9 January) before heading to enter Singapore through the Johor border.

Eight Indonesian students were deported from Malaysia after they were caught  carrying Isis flag images and other Isis content in a mobile phone - File photo Reuters