Defiant protesters targeted China's President Hu Jintao in Hong Kong on Sunday as the former British colony swore in a new leader and marked the 15th anniversary of its return to Chinese rule.

"I vow to defend the Hong Kong... Basic Law," said new chief executive Leung Chun-ying, a millionaire property consultant seen as close to China's communist rulers, as he read out the oath before shaking hands with Hu.

The Basic Law is Hong Kong's mini-constitution, which guarantees the former British colony civil liberties unheard of on the mainland under the "one country, two systems" model set up when it returned to Chinese rule in 1997.

But Hu's visit and the inauguration came as discontent towards Beijing surges to a new post-handover high in Hong Kong, and security has been stifling for the events, with hundreds of police and giant barricades deployed.

Even so as the president began his own speech to around 2,300 guests in a harbour front convention hall, a protestor repeatedly shouted 'End one-party rule'

The man also referred to the crushing of democracy protests on Tianamen Square in Beijing on June 4, 1989, and was rapidly surrounded and taken away as the audience drowned him out with extended applause for Hu's opening remarks.

The Chinese president said that Beijing's support for 'one country, two systems' and the right of the people of Hong Kong to rule the territory was 'unwavering'.

"We will follow the Basic Law... to continue to advance democratic development in Hong Kong," said Hu, who will step down as part of a once-in-a-decade leadership transition in Beijing starting later this year.

But Hong Kong does not get to choose its leader by universal suffrage yet, and Leung was elected as chief executive in March by a special committee stacked with pro-Beijing business elites.

Protestors have been demanding greater democracy and railing against Beijing's meddling in local affairs.

Ahead of the inauguration, a group of demonstrators outside a nearby building burned Leung's portrait, shouting: "Battle the Communist Party! We will battle to the end!"

In another protest, marchers held aloft a mock red coffin emblazoned in Chinese: "The Liaison Office (Beijing's representative) governs Hong Kong."

Hu -- who said Friday he hoped to 'walk more' and 'understand the life and expectations of the Hong Kong people' -- had earlier been expected to attend a flag-raising ceremony on the city's iconic waterfront.

But his absence was noticeable as three helicopters trailed the Chinese and Hong Kong flags in a flypast over the city's harbour, the national emblem in front and at least four times larger, and a flotilla of boats steamed past.

The Chinese leader was expected to leave the city around noon (4 am GMT), just before tens of thousands of Hong Kong people take to the streets at an annual rights rally.

On Saturday police used pepper spray to push back a few dozen demonstrators who tried to get past barricades more than two metres (6.5 feet) high at rallies near Hu's hotel.

A Hong Kong reporter was also briefly detained by police after shouting a question about Tiananmen at Hu.

Anger has been heightened by the death of Li Wangyang, a leading Chinese dissident whose body was found in his hospital ward in China in June. His family say he died in suspicious circumstances.

China's rise has helped spur impressive economic growth in Hong Kong and boost the city's status as a key financial hub, but tensions are growing between the seven million locals and their northern neighbours.

Hong Kongers accuse an influx of newly rich Chinese mainlanders of everything from pushing up property prices to monopolising school places, maternity beds and even baby milk formula.

A poll released by the University of Hong Kong last week showed mistrust among Hong Kongers toward Beijing at a new post-handover high of 37 per cent.

Another survey by the university this week showed the number of Hong Kong people who identify themselves primarily as citizens of China has plunged to a 13-year low.

Discontent against the local authorities is also intense.

Leung, 57, takes over the city at a time of complaints about a widening gap between rich and poor, as well as rising property prices putting home ownership out of reach for many, and has promised to tackle the grievances.

"If we work together, I am sure Hong Kong -- the Pearl of the Orient -- will sparkle again," he said in his speech.