HONG KONG (Reuters) - China’s number three official Zhang Dejiang said in Hong Kong on Wednesday that Beijing was aware of problems in the city but would respect Hong Kong’s autonomy as protesters hit the streets to oppose Chinese attempts to squeeze local freedoms.

Zhang’s visit, which comes at a time of mounting political tensions in Hong Kong, is the first by a senior state leader since tens of thousands of people mounted a massive but ultimately unsuccessful push to pressure Beijing to grant full democracy during the ‘Occupy Central’ street protests in late 2014.

Thousands of police were deployed across Hong Kong, preventing protesters from coming near Zhang as he toured a science park and a harbour front exhibition centre where he addressed an economic summit.

“The argument that the Central Government is trying to turn Hong Kong into mainland (China), or to turn ‘one country, two systems’ into ‘one country, one system’ is totally baseless,” Zhang said during an evening banquet, in unusually direct comments from a state leader on recent challenges and tensions in Hong Kong.

Zhang also addressed the trend of more radical activists forming political groupings and staging disruptive protests to call for greater Hong Kong nationalism and even independence from China; an issue that might become more mainstream when city-wide legislative council elections are held in September.

The idea of Hong Kong independence is anathema to Beijing, which fears any separatist or sweeping democratic demands spilling into China to undermine its rule.

Zhang conceded that a small minority of people in Hong Kong had been calling for independence, but said China would “unswervingly” maintain the current “one country two systems” model of governance for Hong Kong, that guarantees a high degree of autonomy in Hong Kong since it switched from British to Chinese rule in 1997.

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While the recent suspected kidnapping of a bookseller in Hong Kong by Chinese security agents had undermined public and diplomatic confidence in the city’s autonomy, Zhang stressed the rule of law was a “core value” and that if this bottom line was compromised, “how do we continue the prosperity and stability?”

A feature of Zhang’s trip has also been repeated pledges of a more engaged Beijing actively listening to public concerns about Hong Kong’s core relationship with China.

“For the problems that are being exposed now, some are new and some have been around for years and there won’t be an immediate solution. But we can’t question, feel hesitant, or even deny ‘one country, two systems’ because of that,” Zhang said.

Despite a massive police presence, small, scattered groups of protesters took to the streets at various locations to demand Beijing respect the city’s freedoms. A massive yellow banner was unfurled from a hilltop demanding full democracy, while others held up black banners calling for China to end its “dictatorial rule” and to “stop interfering with Hong Kong affairs”.

A few others burnt a portrait of Zhang and called on him to “get the hell out of Hong Kong”

Some pro-Beijing groups, however, denounced the democracy activists for jeopardizing Hong Kong’s economic interests by opposing Beijing, and held up blue banners with the words: “Oppose splitting up Hong Kong.”

Zhang, the head of China’s parliament, the National People’s Congress and Beijing’s point person on Hong Kong affairs, leaves Hong Kong on Thursday.