An Islamist extremist group has declared it wants to enforce Sharia law right across Indonesia, Australia's nearest major Asian neighbour.

Hizb ut-Tahrir's Indonesian spokesman Ismail Yusanto told an Australian camera crew it would fight for a national Islamic legal system where people are caned 100 times for having sex outside of marriage.

'This our duty. Not our ambition. It is our duty. Religious duty,' he told the ABC's Four Corners program.

Scroll down for video

Hizb ut-Tahrir's Indonesian spokesman Ismail Yusanto wants Sharia law enforced nationwide

A woman in Indonesia's Aceh province is caned in public in March for spending time with a man who wasn't her husband

Hizb ut-Tahrir's spokesman in Uthman Badar confirmed he supported death for ex-Muslims

Asked if Hizb ut-Tahrir would succeed, he said: 'We hope and we will try.'

Adulterers have been increasingly caned since 2004 in the Aceh province where Sharia law is practised under an Islamic criminal code which secular Muslims reject.

The province began implementing Sharia law after being granted autonomy in 2001 as the national government in Jakarta tried to quell a long-running separatist insurgency.

Sharia law police patrol the province to ensure women are dressed modestly and unmarried couples aren't sitting too closely together.

Islamist protesters put red paint on an effigy of Jakarta's former Christian governor Ahok

In February, a woman collapsed in pain as she was publicly caned, with a man collapsing on stage two weeks later as he was whipped for having sex outside of marriage.

A woman was given 100 lashes in March for the same offence under Sharia law.

Hizb ut-Tahrir was banned in Indonesia in May after it helped to orchestrate protests against a Christian governor of Jakarta, Basuki Tjahaja Purnama - also known as Ahok, for suggesting the Koran allowed Muslims to vote for him as a Christian.

That was also the same month an Indonesian court has sentenced him to a two-year prison term for blasphemy as Islamist fundamentalists campaigned to have Christians barred from seeking public office in the world's biggest Muslim-majority nation.

Islamic Defenders Front members burn an effigy of a Buddhist monk outside an embassy

Hizb ut-Tahrir, however, remains legal in Australia despite its leader Uthman Badar telling a Bankstown forum in March he supported the death penalty for ex-Muslims.

It is also banned in The Netherlands and Germany and a range of Muslim-majority nations including Pakistan, Bangladesh and Saudi Arabia.

Sharia law is more severe in other parts of the Muslim world, such as Saudi Arabia where thieves have their hands chopped off.

Gays are killed in Saudi Arabia, Somalia, Sudan, Iran, Yemen and Nigeria but not in Indonesia, where same-sex acts are illegal.