Hong Kong pro-democracy campaigners have returned to the streets erecting barricades and other obstacles in protest against the Beijing-backed administration, following overnight clashes with riot police.

As many as 9,000 protesters are estimated to have taken to the streets in the congested district of Mong Kok despite repeated attempts by the police to disperse the crowd with pepper spray and baton charge.

The densely populated district has become a flashpoint of protests in the past several weeks.

The police had earlier cleared the protest areas tearing down tents and canopies but on Saturday morning, most of the streets have been retaken by the campaigners.

The Occupy group said the dawn operation, one of the biggest by the police as yet, has stoked "a new wave of occupations and worsened relations between police and citizens".

"The government's use of 'removing obstructing materials' as an excuse to clear occupied zones will only push the resentment from occupiers and citizens who support them into a vicious circle and dead end, it is totally unhelpful in solving the problem.

"What needs to be condemned is the fact that even as a chink of light appeared for dialogue between the government and the students, Chief Executive Leung Chun-ying took a hard-line and stressed that dialogue does not mean no clearance – thereby creating an obstacle to dialogue."

There are large numbers of protesters and police in other areas such as Admiralty as well, but there have been no clashes so far.

The fresh protests follow the arrest of 26 people overnight on suspicion of assault and criminal damage. According to the police, 15 officers were injured in the skirmishes.

"The police have no right to throw us out. We are just here to take back what is supposed to belong to us," Fish Tong, a 20-year-old student protester, told Reuters.

The protesters are demanding deeper political reforms in the semi-autonomous region giving Hong Kong a free hand from China.