Archbishop Emeritus Desmond Tutu has called on all who believe in democracy to support the people of Hong Kong in their protests, his foundation said on Wednesday.

"I salute the courage of the hundreds of thousands of Hong Kong citizens who have participated in mass demonstrations in the territory in recent days to assert peacefully their right to have a say in the election of their leaders," Tutu said in a statement.

"Their struggle is one that all who believe in the principles of democracy and justice should support."

The Deutsche Presse-Agentur on Wednesday reported that thousands of pro-democracy demonstrators were blocking major roads in various districts of Hong Kong, continuing a protest that began Sunday.

In the early hours of Wednesday, protesters extended their demonstration to Tsim Sha Tsui, a popular tourism and shopping district.

Protesters are demanding reforms ahead of the 2017 elections, including the public nomination of candidates for next chief executive.

Tutu said peaceful demonstrations presented opportunities for various points of views to be ventilated, and for parties to demonstrate their commitment to the principles of freedom of expression, dialogue and rule of law.

He slammed the attack on protesters by law enforcement agencies.

"The firing of teargas at demonstrators, as happened on Sunday, was a bitter blow to what many still hope will be a peaceful, inclusive and dignified transformation process. I pray that the voices of the people of Hong Kong will never be stifled," he said.