SERIKZHAN BILASH, an ethnic Kazakh from China who is a naturalised citizen of Kazakhstan, is a thorn in China’s side. The combative campaigner has helped expose the horrors of China’s gulag to the world: the network of camps in which perhaps 1m people have been interned in Xinjiang province, which borders Kazakhstan. Most of the detainees are Uighurs, Xinjiang’s main indigenous group. Others are Kazakhs and Kyrgyz. All these ethnicities speak Turkic languages and are mainly Muslim, like their kin in neighbouring Central Asia.

When news of the “re-education camps” filtered out in 2017, China flatly denied their existence. It later changed tack, describing them as vocational centres teaching minorities useful skills, as a means to quell religious extremism. Xinjiang has witnessed some violent attacks, amid tensions between Han Chinese migrants and Uighurs, some of whom dream of forming their own separate state. These centres make minorities’ lives more “colourful”, Shohrat Zakir, Xinjiang’s governor, blustered last year, with breathtaking chutzpah. But Mr Bilash’s work over the border in Kazakhstan gave the lie to such blithe justifications. He collected and disseminated disturbing testimony from former internees, who detailed forced indoctrination involving the denigration of the religion and culture of Xinjiang’s minorities.

No longer. On March 10th police in Kazakhstan arrested Mr Bilash, who is now under house arrest facing charges—which he denies—of inciting racial strife. This carries a potential 10-year prison sentence. Prosecutors accuse him of urging “jihad” against Han Chinese. Mr Bilash did call for “jihad” in a recent fiery oration, but specified that he meant an “ideological” battle, not a literal one. Ayman Umarova, his lawyer, deems the case “politically motivated”. Commentators have speculated that Mr Bilash was arrested under pressure from China’s government, which claims he has “ulterior motives to make things up”. Kazakhstan’s government denies that it has ulterior motives of its own, and especially that it is doing China’s bidding.

Mr Bilash’s revelations have placed Nursultan Nazarbayev, Kazakhstan’s president, in a diplomatic quandary, since he does not want to antagonise his mighty neighbour. His government has not condemned the camps explicitly, although Beybut Atamkulov, the foreign minister, acknowledges that there is “pressure” on China’s 1.5m Kazakhs. That is more than Central Asia’s other governments, which have found no fault at all with the treatment of their brethren across the border. Kyrgyzstan’s president, Sooronbay Jeyenbekov, openly admits to not wishing to “spoil relations” with China over the camps. His government has arrested people for participating in anti-Chinese protests. China, after all, is a formidable regional power, the main customer for Central Asia’s energy exports and the builder of much useful infrastructure in the region, as part of its Belt and Road Initiative.

There is already a degree of public hostility towards China in Central Asia, because of its overwhelming economic power. Central Asian governments are not keen to amplify that by allowing the sort of outrage that the internment camps have stirred up in the West. That makes the role of campaigners like Mr Bilash all the more important, and his arrest all the more alarming.