HONG KONG — Hong Kong’s embattled leader attended a flag-raising ceremony Wednesday to mark China’s National Day after refusing to meet pro-democracy demonstrators despite their threats to expand the street protests that have posed the stiffest challenge to Beijing’s authority since China took control of the former British colony in 1997.

Hong Kong Chief Executive Leung Chun-ying took part in the ceremony – marking the anniversary of the founding of communist China in 1949 – as thousands of protesters watching from behind police barricades yelled at him to step down.

China took control of Hong Kong under an arrangement that guaranteed its 7 million people semi-autonomy, Western-style civil liberties and eventual democratic freedoms that are denied to Chinese living on the communist-ruled mainland.

The protesters want a reversal of a recent decision by China’s government to screen all candidates in the territory’s first direct elections, scheduled for 2017 – a move they view as reneging on a promise that the chief executive will be chosen through “universal suffrage.”

The growing protests have attracted worldwide attention, with British Prime Minister David Cameron saying he planned to summon the Chinese ambassador to discuss the dispute.

“It is not for us to involve ourselves in every dot and comma of what the Chinese set out,” Cameron said in England. But he added: “I think it is a critical question. Real universal suffrage doesn’t just mean the act of voting; it means a proper choice.”

Leung’s rejection of the student demands dashed hopes for a quick resolution of the five-day standoff that has forced some schools and offices to close.

Despite the hardening rhetoric from both sides, Tuesday night passed with a festive mood, but the crowds and road blockages are expected to grow sharply as Wednesday and Thursday are public holidays.

It was not clear what the demonstrators planned to do next. There were no official statements from the protesters, who chanted “Jiayou! Jiayou!” – “Keep it up!” – while waving their cellphone flashlights in the dark.