Beijing is poised to declare the Falun Gong an illegal organisation, a move that could spark mass arrests and social instability. More than 25,000 members of the quasi-religious sect besieged government offices in at least 10 mainland cities yesterday in protest at a crackdown on the group. In an internal speech, a senior Politburo member said the Falun Gong was posing a frontal threat to the party's hold on power. Should the 'disorder' caused by sect members spread, Beijing would have no choice but to declare it illegal, he said. The Politburo member had ordered police and People's Armed Police on alert in preparation for possible mass arrests of members who failed to stay off the streets. However, the numbers involved would likely mean an amnesty for those cult members following the authorities' orders. Yesterday thousands of members of the Falun Gong cult tried to protest at Beijing's Zhongnanhai leadership compound against the detention of key members, witnesses said. Police rounded up more than 1,000 people - mostly elderly men and middle-aged women suspected of belonging to the sect - and took them in buses to stadiums on the outskirts of Beijing, witnesses and stadium officials said. Stadium officials last night said there were still 'lots and lots' of Falun Gong followers in a gymnasium complex, but refused to estimate the number. Last night, hundreds of uniformed and plain-clothes police were still lining the Avenue of Eternal Peace leading to Zhongnanhai. Officers stood guard on both sides of the road and riot police were at the ready in lorries parked nearby. Earlier, police buses, vans and motorcycles were parked around the compound and police prevented cars without special permits from using the north-south road beside it, causing traffic jams. They frustrated the sect's attempt to repeat a 10,000-strong protest outside the compound in April, aimed at demanding official status for the group. The SAR-based Information Centre of Human Rights and Democratic Movement in China said at least 30,000 Falun Gong members had been detained nationwide in the past week. About 10,000 of them were rounded up in Beijing. In a letter posted on the Internet, Falun Gong appealed to members to 'protect' the sect by explaining their aims to officials and demanding the release of detained members. About 10,000 members protested at the government headquarters in Guangzhou yesterday. Witnesses said the crowd dispersed peacefully. In Shenzhen, about 800 members were taken by official buses to Hongling Secondary School after they staged a sit-in at 9am. They were locked in the school sports stadium under tight security. 'We came to see if we can explain to government officials who we are and what we are doing,' said Zhang Xiaohua, who took the day off from her factory job in Shajing district. In Shanghai, hundreds of members staged a peaceful sit-in at People's Square in the city centre. Witnesses said they left voluntarily without incident. In Hong Kong yesterday, more than 40 members staged a silent protest outside Xinhua in Happy Valley to urge Beijing to free fellow cult members. In Washington, 150 followers gathered at the Chinese Embassy to show their support.