An Indonesian court Monday jailed three members of China's Uighur minority for six years each after they were caught attempting to join an Islamic extremist group led by the country's most wanted militant.

The court heard that the men were arrested in September on the rugged central island of Sulawesi as they sought to meet militant Santoso, leader of a group known as the Eastern Indonesia Mujahideen.

The group, which hides out in the jungles in an area known as a militant hotbed, is considered one of the few remaining extremist outfits that pose a serious threat in Indonesia and has been accused of deadly attacks on police.

Santoso has also pledged allegiance to the Islamic State group.

Presiding judge Kun Marioso told the North Jakarta district court that Ahmet Mahmut, 20, Altinci Bayram, 29, and Tuzer Abdul Basit, 23, had broken anti-terror laws and were guilty of an "evil conspiracy".

They also violated immigration laws by using fake Turkish passports, he said.

"The defendants came to Indonesia with the intention of joining Eastern Indonesia Mujahideen and carrying out acts of terror," he told the court.

"We sentence the defendants each to six years in prison and a fine of 100 million rupiah ($7,500)," he added.

The sentences were lighter than the seven years sought by prosecutors, as they had no previous convictions.

The men did not speak to reporters after the trial but their lawyer Asludin Hatjani said they were considering whether to appeal the sentence.

A fourth man, who was arrested with them and is facing similar charges, will be sentenced on July 29.

Indonesia is home to the world's biggest Muslim population of about 225 million and has long struggled with Islamic extremism, but a successful crackdown over the past decade has largely dismantled the most dangerous networks.

The mostly Muslim Uighur minority come from the northwest region of Xinjiang, where the group say they face cultural and religious repression.

Many are believed to have fled the restive region in recent years, sometimes travelling through Southeast Asia in the hope of resettling in Turkey.

Hundreds of Uighurs were detained last year for illegally entering Thailand. The Uighurs claimed to be Turkish citizens and 181 have been allowed to go to Turkey with more than 100 others sent back to China last week.

China's security ministry said Saturday that the Uighurs repatriated by Thailand had been on their way to Turkey, Syria or Iraq "to join jihad", state media reported.

The deportations triggered condemnation from rights groups and protests in Turkey over China's treatment of Uighurs.