Jakarta: More terrorist attacks are likely in Indonesia as local Islamic State groups compete to carry out plots and establish their supremacy, terrorism expert Sidney Jones has warned.

Ms Jones said the personal rivalries and power struggles between Indonesian IS supporters portended more violence. She warned foreigners would be back on the terror hit list, along with police officers and Shiite Muslims.

The warning comes as 17-year-old Andika Bagus Setiawan was sentenced to five years' jail for his role in a foiled terror attack timed to coincide with Christmas and New Year celebrations.

Targets for the planned attack, which was directed by Bahrun Naim, an Indonesian who joined IS in Syria in 2015, included the governor of Jakarta, Basuki Tjahya Purnama, better known as Ahok, and high-ranking police officials such as national police chief Badrodin Haiti.

Naim also directed his cell to stab Westerners in the expat precinct of Menteng in Jakarta.

However Ms Jones said the January 14 Jakarta attacks that killed eight people were not masterminded by Naim, despite police initially claiming he was responsible.

She said they are now known to have been carried out locally by a group called Partisans of the Caliphate (Jamaa Anshar Khilafah, or JAK), which is believed to be led from prison by Indonesia's leading pro-IS cleric, Aman Abdurrahman.

"The enormous publicity generated increased the pressure on Aman's rivals to undertake operations in Indonesia as soon as possible," Ms Jones says in the report, entitled "Disunity among Indonesian ISIS supporters and the risk of more violence".

"The competition will produce an increase in terrorist plots that regional law enforcement agencies will be hard pressed to contain."

For example, after the January 14 attack near one of Jakarta's best-known landmarks, the Sarinah department store, Bahrumsyah, another Indonesian based with IS in Syria, reportedly ordered his followers to undertake a similar action immediately.

"The fact that it has become much more difficult to cross into Syria from Turkey means that there will be more potential fighters willing to take on the war at home than in 2014 or 2015," the report says.

More than 215 Indonesians had been deported by Turkey as of December 2015 after trying but failing to cross into Syria. "While some families are still leaving, the message that it is becoming harder is getting through," the report says.

Ms Jones said if the government was interested in targeted deradicalisation programs, it could look at some of these deportees from Turkey, many of whom sold everything they had to try and join IS in Syria.

She also said the government needed to focus more on prisons, where many terrorist plots are hatched.

Proposals included giving specialist training to prison officials in charge of extremists; closely supervising visitors and monitoring their conversations; and increasing surveillance of post-release prisoners.

Andika, the youngest member of Naim's group, was arrested in late December. The court heard he had been asked to prepare explosive materials for bombmaking and plan to attack certain targets.

Judge Simbolon said aggravating factors included hampering the government's program of combating terrorism and the boy's strong intention to carry out the attacks and bombings.

However Andika's lawyer, Nurlan Arman Remi, said it was a severe punishment for a minor when the attack had not even occurred.