Thunder and rain failed to dent pro-democracy protests sweeping Hong Kong, as embattled Chief Executive Leung Chun-ying conceded the movement would "last for quite a long while". Big crowds continued to gather in the city's commercial districts last night despite the sudden downpour. Holding high the umbrellas they used to fend off riot police, protesters sang songs and chanted slogans in the rain. Roads in Admiralty, Wan Chai, Causeway Bay, Central and Mong Kok were transformed into seas of umbrellas - the accidental symbol of Hong Kong's civil disobedience movement that has grabbed worldwide attention. Speaking publicly for the first time since Sunday's botched attempt to disperse the crowds with tear gas, Leung admitted the protests would not end soon. Still, he urged the organisers to call off the protests, suggesting that the movement was getting "out of control" and affecting emergency services. "The [impact] on people's daily lives, their personal safety, the city's economic development and the damage to our international image will grow bigger and bigger," Leung warned. The Federation of Students and Occupy Central - the two main groups behind the protests - announced that they would open up corridors for emergency vehicles to pass when needed. British Deputy Prime Minister Nick Clegg said he had requested an urgent meeting with the Chinese ambassador to London to express his "dismay and alarm" over the handling of the protests. "The Chinese authorities in Beijing seem determined to refuse to give to the people of Hong Kong what they are perfectly entitled to expect, which is free, fair, open elections based on universal suffrage," Clegg said. His comments are sure to anger Beijing, which a day earlier had told foreign governments not to interfere in the internal affairs of China. China Central Television reported the social disturbances for the first time. Without showing any images, it highlighted the disruption caused and said any attempt to force the central government to accept "unreasonable demands" was futile. A mainland researcher familiar with the leadership's thinking said top officials discussed the situation in Hong Kong after Sunday's chaos. "They believe the Hong Kong government can handle the protests on its own. It is highly unlikely that the People's Liberation Army needs to be mobilised." However, the researcher warned Beijing could advise mainland travellers not to come to Hong Kong if the situation deteriorated. Already, some shops in Mong Kok have complained that sales had gone down by 50 to 90 per cent since Monday. Federation of Students leader Alex Chow Yong-kang said protests would escalate if their demands were ignored. They want Leung to step down and Beijing to retract its strict limits on Hong Kong's chief executive election in 2017. Another student group, Scholarism, said members would go to Golden Bauhinia Square today to protest at the National Day flag-raising ceremony. Early this morning, students started gathering at the site in Wan Chai, where about 100 police officers were standing guard. Taiwanese President Ma Ying-jeou said the mainland risked alienating the island's people if it failed to respond with a "delicate hand" to the protests. "If the mainland can handle this with a delicate hand, it can help [bridge] the gaps between people across the Taiwan Strait and benefit cross-strait ties," he said. "Otherwise, it could serve to alienate Taiwanese people,"