China's network of detention centres in the northwest Xinjiang region is much bigger than previously thought and has been expanded in recent years, according to research presented by an Australian think tank Thursday.

The Australian Strategic Policy Institute said it had identified more than 380 "suspected detention facilities" in the region -- where China is believed to have detained more than one million Uighurs and other mostly Muslim Turkic-speaking residents.

The number of facilities is around 40 percent greater than previous estimates and, according to Australian researchers, has been growing despite China's claims that many Uighurs have been released.

Using satellite imagery, eyewitness accounts, media reports and official construction tender documents, the institute said "at least 61 detention sites have seen new construction and expansion work between July 2019 and July 2020."

Fourteen more facilities were under construction in 2020 and around 70 have had fencing or perimeter walls removed, indicating their use has changed or they have been closed.

US lawmakers recently voted to ban imports from Xinjiang, citing the alleged use of systematic forced labour.

Beijing recently published a white paper defending its policies in Xinjiang, where it says training programmes, work schemes and better education mean life has improved.

It has defended the so-called training centres as necessary to stamp out extremism.

Following the publication of the latest report, Chinese government-controlled nationalist tabloid the Global Times cited "sources" saying Australian Strategic Policy Institute contributors Clive Hamilton and Alex Joske were banned from entering China.