In pictures: Fearsome escalation of anti-government demonstrations continue in Hong Kong

A black-clad protestor stands by flames rising from a fire in Hong Kong. Hong Kong protesters threw petrol bombs and police fired tear gas in street battles across the city on Tuesday, posing a direct challenge to Chinese President Xi Jinping on the 70th anniversary of the founding of the People's Republic.

Demonstrators stand around a burning barricade during a protest in the Sham Shui Po district of Hong Kong.

Protesters run from police during clashes in the Wanchai district in Hong Kong.

Protesters trash a local government office during a demonstration in the Sham Shui Po area in Hong Kong.

Protesters react from tear gas fired by riot police in the Sham Shui Po district of Hong Kong.

Protesters take cover in Hong Kong.

A man is detained by police during clashes in the Wanchai district in Hong Kong.

An anti-government protester sets fire to a barricade in Sham Shui Po district, on China's National Day in Hong Kong.

Protesters trash a local government office during a demonstration in the Sham Shui Po area in Hong Kong.

An anti-government protester sprays graffiti on a government building in Sham Shui Po district, on China's National Day in Hong Kong.

Black-clad protestors stand by the entrance of a closed public transport gate in Hong Kong.

An anti-government protester throws a brick at a government office during a protest in Sham Shui Po district, on China's National Day in Hong Kong.

An anti-government protester runs through a cloud of tear gas during a protest in Sham Shui Po district, on China's National Day in Hong Kong.

An anti-government protester takes cover under an umbrella during a demonstration in Sha Tin district, on China's National Day in Hong Kong.