Four Chinese men arrested by counterterrorism police have been formally named as suspects and detained for allegedly violating anti-terrorism and immigration laws, said Indonesia's National Police Chief General Sutarman.

Regulation cracks down on hoax threats Hoax threats of bombs, radiation and hijacking of aircraft will be treated as acts of terror by police and judicial authorities, according to a new regulation unveiled on Sunday. The notice on legal references on handling violence, terrorist and extremist religious cases, jointly released by the Supreme People's Court, the Supreme People's Procuratorate and the Ministry of Public Security, stipulates that making hoax threats of bombs, biochemical weapons, radiation, hijacking of aircraft or natural disasters will bring punishment for faking terrorist information. Those who are aware of the threat being a hoax and who try to spread the information will also be punished, the regulation said. Faking or spreading hoax threats that cause major social turbulence will bring harsher punishment, it said. The notice gave detailed guidance on the principles of handling terrorist acts of different kinds, defining the nature of cases and the criteria for defining cases in accordance with criminal law. It aimed to punish activities of violence, terrorism and religious extremism and prevent such cases from happening. According to the notice, broadcasting or sharing contents of religious extremism, terrorism and violence through websites, online forums, instant messaging tools and cellphone applications is punishable for the offense of splitting the State. Displaying, selling, designing or producing badges of religious extremism or terrorism is also punishable for the same offense. The notice was unveiled after a number of hoax threats to hijack jetliners were made in recent years. In August of last year, police in Hubei province detained a 17-year-old boy who allegedly made a bomb hoax call that disrupted airport traffic because he "felt bored". The boy called Yichang Sanxia Airport, claiming his friend was in a taxi to the airport carrying knives and explosives. In October, police in Changsha, the capital of Hunan province, detained another suspect who allegedly made false bomb threats that affected four flights leaving and bound for Changsha.

The four, whom police identified as ethnic Uygurs from the Xinjiang Uygur autonomous region, were arrested on Sept 13 and will be formally charged at a later date.

A counterterrorism investigator said the four had enrolled in a terrorist training camp in Poso run by the Eastern Indonesia Mujahidin, news website Beritasatu.com reported.

Eastern Indonesia Mujahidin is led by Santoso, a wanted militant who in July pledged allegiance to the Islamic State in Iraq and Syria, in a widely circulated video.

"They wanted paramilitary training and to learn how to assemble bombs and weapons with Santoso's group, before returning to their country to put that into action," the investigator said.

The arrest marked the first time that radicals from Xinjiang have tried to connect with their Indonesian counterparts, and raises concern that even as developments in the Middle East are rekindling old militant networks, new ones may be forming.

Chinese Foreign Ministry spokesman Hong Lei said on Wednesday that China is verifying reports that the four people were detained by Indonesian police.

He said the East Turkestan Islamic Movement does not only plot attacks in China, but also works with other terrorist organizations to disturb regional and world stability, so fighting ETIM is part of the overall international efforts to counter terrorism. China appreciates the understanding and supports in China's efforts to fight ETIM and hopes to strengthen the cooperation.

ETIM, which seeks the separation of Xinjiang from China and the establishment of an East Turkestan, has been proved to be behind many terrorist attacks in the country.

The ministry was not available for comment on Sunday.

Terrorism analyst Al Chaidar said: "This suggests Santoso's message has traveled. His mention of a transnational jihad has also moved and affected some to act."

The four men were carrying false Turkish passports, which identified them as Abdul Basyit, 19, Ahmed Bozoghlan, 28, Atlinci Bayram, 19, and Alphin Zubaidan, 27.

Sutarman said earlier that they bought these passports for $1,000 each in Thailand, from where they flew to Kuala Lumpur, and then to Bandung, West Java. They took another flight to Makassar, South Sulawesi, where three other men who were also arrested picked them up.

Police on Friday released two of those arrested, saying they were just drivers. But the third man, Syaiful Priyatna, a 29-year-old teacher, was detained for having harbored a fugitive.

Two other suspects were also detained in Palu on Sept 15 in connection with the case－Akbar, who owned a house where the four stayed, and Kalman, a member of Santoso's group.