Prakash was arrested in Turkey in 2016 after crossing from Syria. He later admitted partial blame for Islamic State group terror plots in Australia.

In May last year, Australian PM Malcolm Turnbull said he expected Prakash to be extradited "within months".

He is now likely to face charges in Turkey, reported News Corp Australia.

The Australian government has said it is disappointed by the Turkish judge's decision in the Kilis Criminal Court.

What is Prakash accused of?

Australian authorities have said that Melbourne-born Prakash is linked to failed terror plots in Australia and calls for lone-wolf attacks against the US.

In 2016, the government described him as "the principal Australian reaching back from the Middle East" into networks in Melbourne and Sydney.

When asked whether he was responsible for plots in Australia, Prakash told a court last year: "I had something to do with [it], but I was not 100% responsible."

He alleged that he had been forced to make IS propaganda videos, and that he had fled the group after seeing its "true face".

In Australia, he faces charges of being member of a terrorist organisation, as well as supporting and promoting the group.

What did the court say?

Judge Ismail Deniz denied the prosecution's extradition request after saying its conditions had not been made available to the court, according to the Australian Broadcasting Corporation.

The judge did not give further reasoning, the report said.

The court then ruled that Prakash would remain in custody to answer terrorism allegations in Turkey, News Corp Australia reported. The case will resume in September.

How has Australia reacted?

Mr Turnbull said his government would not rule out appealing against the extradition decision.

"Our goal is to ensure that Neil Prakash is not ever able to practise his evil trade of terrorism ever again," he said.

However, Mr Turnbull added that the Turkish government was "equally determined to deal with him".

Turkey's foreign ministry in Istanbul did not immediately comment, news agency Reuters said.