Islamic State (Isis) militants returning to China's predominantly Muslim Xinjiang region have been arrested, said a Chinese government official.

"I believe there are extremists from Xinjiang who have joined Islamic State," said the Communist party's chief in the region, Zhang Chunxian, at the party's annual congress in Beijing.

"We have recently arrested some groups who have returned after joining," he said, without giving details, reports the South China Morning Post.

About 300 Chinese nationals are believed to have travelled through Malaysia to join IS in Syria and Iraq, the country's Home Minister Ahmad Zahid Hamidi said in January, where IS controls large areas of territory.

Earlier this year, the Chinese Global Times reported that three Chinese nationals had been killed trying to leave the group after becoming disillusioned.

A Kurdish official told the tabloid that one man had been shot in Syria in September after trying to leave the group and return to the university he was attending in Turkey, and two others had been beheaded along with 11 others from six countries after attempting to leave.

Beijing alleges that separatist group the East Turkestan Islamic Movement has launched terrorist attacks in Xinjiang, which is home to the Muslim Uighur people who claim they are persecuted by the Chinese government.

Beijing has previously said that it believes that separatist militants from Xinjiang have trained with IS.

Last year, Uighurs were alleged to be responsible for a knife attack at a Kunming train station, in Yunnan province, that left 33 dead and 143 injured, after failing to leave the country "to participate in jihad", according to a Communist Party spokesman.

Zhang said that authorities in Xinjiang would work to counter the influence of IS.

"Xinjiang cannot stay out of the affair," he said. "We are also affected."