Singapore authorities have called for increased vigilance on Saturday, 6 August, after Indonesian police arrested a group of men who were believed to be planning a rocket attack on the city-state. The men were reportedly planning the attack with the help of Syrian-based Islamic State (Isis) terrorists.

Six suspected militants were detained on 5 August during raids in Batam Island, which is located 15km south of Singapore. Police believe that the men were planning to launch rockets into Singapore from the island. The men are being held there while investigations continue.

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Kasiviswanathan Shanmugam, Singapore's Home Affairs Minister, wrote on Facebook: "This shows how our enemies are thinking of different ways of attacking us. Terrorists who will seek to come in through our checkpoints; they will also try to launch attacks from just outside. And this is in addition to lone wolf attacks from radicalised individuals [and] groups. We have to be extra vigilant."

He announced that Prime Minister Lee Hsien Loong will launch the SG Secure national movement next month, which will seek to mobilise the entire community into being "more security conscious" and involved in the fight against terrorist attacks. The SG Secure movement was launched by authorities in response to a "steadily increasing" terrorism threat to Singapore, describing the threat situation against Singapore as "serious".

Authorities have identified the leader of the arrested group as Gigih Rahmat Dewa, with local media reporting that he is a 31-year-old factory worker from the Javanese city of Solo. However, authorities have said that they have not yet discovered any physical evidence of a rocket attack.

Batam District Police Chief Helmi Santika told Reuters that they are studying the materials that the arrested group had, but have only seized weapons, including arrows, long-range firearms and pistols. The group is also suspected to have direct links to Bahrun Naim, an Indonesian who used to live in Soho but is now believed to be fighting with IS (Daesh) terrorists in Syria.

National Police Chief Tito Karnavian said: "The six people led by GRD had planned to launch attacks. They were in direct contact with Bahrun Naim in Syria and he had ordered them to attack Singapore and Batam."

Investigators in Indonesia believe that Naim was one of the masterminds behind January's attack in the Indonesian capital of Jakarta that killed eight people, including the four attackers. Following the Paris attacks in November 2015, Naim wrote a post online urging his Indonesian followers to study the planning, targeting and timing of the terrorists who killed 130 people in France.