THOUSANDS of Hong Kong college and university students have boycotted classes to protest against Beijing's decision to restrict electoral reforms.

The boycott is the start of a week-long strike marking the latest phase in the battle for democracy in the former British colony.

The strike comes as dozens of the city's tycoons and business leaders visit Beijing to meet China's communist leaders, who are seeking to bolster support among Hong Kong's elite for the central government's policies on Hong Kong.

Student organisers are dismayed over Beijing's decision in August to rule out open nominations for candidates under proposed guidelines for the first-ever elections to choose Hong Kong's top leader, promised for 2017.

China's legislature insists candidates be vetted by an elite committee similar to the body of mostly pro-Beijing elites that has until now selected the city's leaders.

The battle over democracy in Hong Kong has led to an increasingly tense and divided city, with activists threatening to stage a mass "occupation" of the Asian financial hub's central business district as part of a civil disobedience campaign to press their demands.

When China took control of the former British colony in 1997, it agreed to a mini-constitution that guarantees Hong Kong can keep civil liberties unseen on the mainland, while also promising the leader can eventually be chosen through "universal suffrage".

But Beijing's insistence candidates be screened for patriotism to China has stoked fears Hong Kong will never get genuine democracy.