Protest crowds in Admiralty swelled into the thousands last night and student leaders called for a "long-term Occupy" as Hong Kong's top leaders prepared to leave the city for a regional forum in Guangzhou. Watch: Timelapse: thousands join rally as students vow to escalate protests - Occupy Hong Kong Day 13 Supporters of the Occupy movement returned to the streets in a massive show of support after the government scrapped a promised dialogue with students. The crowds at the main rally site in Admiralty swelled to tens of thousands, organisers said. A police estimate was not immediately available. Student group Scholarism - one of the organisers - called on supporters to occupy "every inch of the streets". Tensions flared after the government on Thursday scrapped a meeting with student leaders scheduled to take place yesterday. Both sides accused the other of lacking sincerity. Piano teacher Kit Lau said she came out because she was upset by the government's abrupt cancellation of the meeting. Another teacher, Gray Chow, said: "People are even more disillusioned with the government now." On the mainland, a People's Daily commentary questioned why student leaders had returned to their demand for Beijing to retract the framework it set out for electoral reform. "We cannot help but wonder whether some people with an ulterior motive are behind this. It sabotaged a good chance to end the turmoil … But people who play with fire will eventually get burned," it said. Premier Li Keqiang , in Germany to meet Chancellor Dr Angela Merkel, said he was confident that "social stability" could be preserved in Hong Kong and stressed that Beijing would not change its "one country, two systems" approach to the city. Merkel hoped the demonstrations remained peaceful. Chief Secretary Carrie Lam Cheng Yuet-ngor and three ministers head to Guangzhou today to attend a regional integration forum. Chief Executive Leung Chun-ying will attend tomorrow. While Lam will return tomorrow, Leung and the other ministers are scheduled to be out of town until Monday afternoon - leaving an understrength government at a time of crisis. Some pan-democrats tried to reopen dialogue with the government but were told students must soften their stance. A pan-democrat source said they understood it was not Lam's decision to cancel the talks. A government source expected the Occupy protests to drag on for another two weeks. The impasse could prove costly all round, with both sides facing increased criticism for their handling of the protests. Basic Law Institute chairman Alan Hoo SC slammed the government for lacking the courage to solve the stand-off. He said the government should inform Beijing that it would withdraw its application for reform if the public strongly opposed the proposal. "I don't see the Hong Kong government has the courage to do that," Hoo said. Several pro-establishment lawmakers went to Government House last night to meet Leung and Lam. Tam Yiu-chung, leading of the Democratic Alliance for the Betterment and Progress of Hong Kong, said they urged Leung to find a solution to end the deadlock with students, but "we did not say the time is ripe to clear the protest area". He said Leung agreed with their ideas, without giving details.