The Guangdong authorities have detained at least three influential labour rights activists in a wide-ranging crackdown amid the mainland's economic slowdown and escalating industrial tensions. According to official reports by the Guangzhou public security department, labour rights activists Zeng Feiyang and Zhu Xiaomei were placed under criminal detention for allegedly "gathering a crowd and disturbing public order" in a facility in the city's Baiyun district late on Friday evening. Another notice issued by Foshan public security said that activist He Xiaobo was placed under detention for alleged embezzlement in a Nanhai facility on Friday afternoon. The Hong Kong-based China Labour Bulletin said the whereabouts of five other labour right activists, including Peng Jiayong, Meng Han, Deng Xiaoming, He Minghui and Bei Guo, remained unclear, while a few other activists and workers were released on Friday after being questioned. This is the largest crackdown targeting labour rights activists in recent years. It follows a nationwide crackdown against rights lawyers in July when at least 248 people were taken away, detained or arrested. As China's economic growth slows, tens of thousands of migrant workers in Guangdong province have staged protests over the past months demanding that employers settle unpaid social insurance payments before closing down or relocating to more remote regions away from the Pearl River Delta. Mainland labour NGOs provide a service upholding workers rights that the government-affiliated All-China Federation of Trade Unions fails to provide, but they remain in a legal grey area because they are denied official registration as NGOs. Zeng, director of the Guangdong Panyu Migrant Worker Centre, based in Guangzhou, is considered one of the mainland's most prominent labour rights activists and won an award in recognition of his work in 2012. Over the past 12 months, labour rights activists have faced unprecedented assaults and harassment for helping workers fighting for their legal rights. Zeng told the Post in an interview before this year's Labour Day that local activists were bracing themselves for a tough year ahead, citing an increasingly challenging working environment. "I think I might be locked up sooner or later within the year," he said. Zeng himself was assaulted by four men after they stormed his office last December. The crackdown against Guangdong labour activists has been criticised by academics and the labour sector, with the China Labour Bulletin saying the crackdown "would only further aggravate tensions between labour and management". Professor Pun Ngai, a labour issues expert in Hong Kong Polytechnic University's department of applied social sciences, has called on the mainland government to support and monitor the services provided by labour rights NGOs, while strengthening the function of governmentaffiliated unions as fundamental strategies to resolve labour tensions.