Disagreements over extremists Islamic State in Iraq and Syria ( ISIS ) are causing rifts among hardliners in Indonesia and eroding the authority of jailed cleric Abu Bakar Bashir.

Bashir's sons recently quit their father's founding extremist organisation Jamaah Ansharut Tauhid (JAT), rather than take an oath of allegiance to ISIS, according to the Jakarta Post.

Bashir, serving a 15-year prison sentence at Nusakambangan ordered all JAT members who do not support ISIS to leave the organisation.

The sons, Abdul Rohim(also known as Iim) and Rosyid Ridho, formed splinter group Jamaah Ansharusy Syariah (JAS), which boasts 2,000 supporters, according to the Post.

That group still poses a national security threat according to Ansyaad Mbai, head of the National Counterterrorism Agency (BNPT), which added JAS to its list of terrorist organisations.

"If they say the purpose is to step away from JAT to establish sharia law, what is the difference between the two? The more important question is how they will achieve their goal," Ansyaad said.

"We will continue our law enforcement efforts regardless of the addition of new organisations. Citizens' safety is more important."

"I really do not see what makes JAS different than JAT, except that JAS refused to take the ba'iat (oath of allegiance) to ISIS's leader, Abu Bakar al-Baghdadi ," college student Iryana Multi told Khabar.

Terrorism expert Noor Huda Ismail said the two organisations share the same ideology.

"We all know that most terrorism action in Indonesia is supported by Islamic radicals – including Jemaah Islamiyah (JI), JAT, the Eastern Indonesia Mujahideen (MIT) – and they all have a similar a goal: establishing a new Islamic state but not within democracy. JAS seems to accommodate this ideology," Noor, chairman of the Institute for International Peace Building, told Khabar.

According to University of Indonesia terrorism expert Wawan Purwanto, establishment of JAS could bring negative consequences.

"It can be a place where terrorists reconnect to strengthen their goals and share resources," Wawan told Khabar. He urged the government to enlist the support of communities "so they can closely engage in terrorism prevention".