Authorities in China have issued an emergency security alert as thousands of military veterans were expected to converge on Beijing ahead of a key conference in May in a bid to highlight grievances like unpaid pensions, campaigners told RFA on .



People's Liberation Army (PLA) veterans have staged repeated mass protests in recent months over pensions, healthcare and other demobilization benefits they said were promised but not delivered.



Wearing their uniforms from units and division across the PLA's three services, the veterans have previously gathered en masse outside the party's military arm, and the graft-busting Central Commission for Discipline Inspection (CCDI), calling on President Xi Jinping to address their grievances.



"We have been advised by the stability maintenance office of the [Tianjin] municipal council that former PLA volunteers will be gathering for a mass petitioning event in Beijing up until ," two separate versions of the urgent alert leaked online from Tianjin's Ninghe district and from Chengcheng county in the northern province of Shaanxi warned.



"We are asked to work with this group to achieve a target of zero [petitioners] going to Beijing," one notice warned.



"We must implement strongly effective measures and carry out stability maintenance work," the other said. "Secrecy will be maintained." The measures were dated and hold effect until , when China hosts a regional forum on its Central Asia land bridge known as One Belt, One Road.



Some veterans told RFA they had already arrived in Beijing, however, while rights groups said dozens have already been detained.



"I saw a large group of disabled veterans in Beijing , where security is extremely tight," a veteran who declined to be named said.



"The Beijing police have stepped up their controls, and several dozen veterans were taken away from Changping, where a lot of the veterans stay," he said. "A lot of them are incommunicado so I think something has happened to them, that they have been locked up."



"There was some talk of getting to Beijing ahead of the International Workers' Day celebrations on , but I haven't seen that many people here," he said.



Some 60 soldiers taken to detention center

China announced last week that 28 countries will send their heads of government to its Belt and Road conference on -15 in Beijing.



According to the Civil Rights and Livelihood Watch rights website, at least 60 PLA veterans were taken to the Jiujingzhuang unofficial detention center on the outskirts of the capital on , with many more out of contact after being taken to local police stations in various suburbs of Beijing.



A veteran surnamed Shao said the veterans are calling on the authorities to abide by promises made to them before they signed up to fight in China's short border war with Vietnam in 1979.



Clause 3 of the Military Pensions Priority Regulations requires governments to ensure that the standard of living and social situation of demobilized PLA soldiers doesn't fall below the national average.



"I am disabled, and I have been left with nothing," Shao told RFA. "Most of the veterans are disabled because of injuries sustained on active duty."



"The youngest of them are about 50 now, while the oldest are in their sixties and seventies," he said. "They have arms and legs missing, and they are all in great hardship when it comes to meeting their medical bills and their accommodation costs."



"Some are in dire poverty, with no support net whatsoever," he said.



A second veteran who asked to remain anonymous said the authorities appeared to be censoring social media platforms for any posts linked to veterans' protests.



"We were discussing what to do [via social media] and we got shut down by the government," the veteran said. "If there are too many people, they won't let you go."



"Some people have already been escorted home by interceptors [from their hometowns]," he said. "The authorities have already figured out what is going on from reading our posts and listening to our phone calls."



"A lot of people tried to get to Beijing but didn't make it."

House arrest for some soldiers



Shandong veteran Ling Zaifu said he is stuck at home under virtual house arrest with his telephone calls being monitored.



"Anyone who goes to lodge a complaint will find themselves under surveillance," Ling told RFA. "I even saw the relatives of a comrade of mine who is a veteran of nuclear testing being watched and followed."



"I have been under round-the-clock surveillance for several years now, and they follow me if I go out," Ling said. "But they shut down my QQ [chat account] a week ago, as they have with anyone who tries to stand up for their rights."



"Anyone who calls me on the phone gets a visit from their local stability maintenance office for a 'chat'," he said.



And Qingdao veteran Xinggan said he doesn't know if he will make the mass petitioning event on .



"There is tight security everywhere now, so they won't let me go," said. "We are all under restrictive measures, and we have to file a report whenever we leave or arrive back in town."



"People follow me everywhere."



Veterans have staged a string of silent protests over their retirement benefits since a mass protest on Oct. 11 shocked the authorities, who ordered provincial chiefs to Beijing to begin escorting the disgruntled protesters home.



A protest last February outside the CCDI also highlighted local governments' failure to deliver promised pension, medical and social security benefits to demobilized PLA soldiers, regarded by Beijing as one of the country's most politically sensitive groups.



While officials from the Central Military Commission (CMC) ordered provincial and city leaders to Beijing to address the crisis, the veterans say promises that changes would begin to be implemented from Jan. 1 haven't been kept.



Reported by Wong Siu-san and Sing Man for RFA's Cantonese Service, and by Xin Lin for the Mandarin Service. Translated and edited by Luisetta Mudie.