Thousands of pro-democracy protesters have taken to the streets of Hong Kong for the first time since mass demonstrations shut down parts of the city for more than two months.

A sea of yellow umbrellas - the symbol of the campaign - moved slowly through central Hong Kong with crowds shouting for "true universal suffrage".

Some 2000 police flanked an estimated 12,000 protesters marching on the city's glitzy shopping and financial districts, seeking to avoid a repeat of the so-called Occupy Central campaign that saw demonstrations shut down key roads for two-and-a-half months months.

Last year's protests for a fully democratic vote to choose Hong Kong's next leader were the most serious challenge to China's authority since the 1989 pro-democracy demonstrations and crackdown in Beijing's Tiananmen Square.