HONG KONG (REUTERS) - Police kept a close watch over central Hong Kong as the Asian financial hub returned to normalcy on Friday (June 14), with banks reopening branches closed during violent protests against a proposed extradition Bill with mainland China.

But with the city's government showing no signs of backing down over the controversial Bill, which critics warn threatens Hong Kong's rule of law, further demonstrations are planned.

A few dozen demonstrators remained near the city's legislature on Friday, which had been scheduled to debate the Bill this week but was thwarted when thousands of protesters took to the streets and blocked the building.

Police, who fired tear gas and rubber bullets into the crowd, have been criticised for using excessive force on unarmed demonstrators.

Opponents of the proposed extradition Bill fear it would undermine Hong Kong's rule of law that underpins its status as an international financial hub.

Hong Kong stocks ended Friday morning with further losses, extending this week's sell-off fuelled by concerns over protests that hit this city as well as China-US trade war uncertainty.

The Hang Seng Index fell 0.52 per cent, or 141.08 points, to 27,153.63 by the break.

The territory's Beijing-backed leader, Chief Executive Carrie Lam, has stood by the Bill, arguing that it is necessary to plug loopholes that allow criminals wanted on the mainland to use the city as a haven. She has said the courts would provide human rights safeguards.

On Friday, HSBC and Standard Chartered Bank reopened branches that had been closed near where the protests erupted.

Businesses were operating normally and commuters flowed through the area to work.

Hong Kong authorities have closed government offices in the city's financial centre for the week due to the unrest.

On Thursday, Hong Kong Police Commissioner Stephen Lo said police had arrested 11 people and fired about 150 tear gas canisters at the crowd during protests on Wednesday. The city's hospital authority said 81 people were injured in the protests.

Police also later arrested two students at the University of Hong Kong after a raid on a student hall of residence, according to an official at the university. The police gave no immediate response to Reuters inquiries on what charges the students face.

Despite the calm on Friday, more protests loom this weekend.

Last Sunday, a march against the extradition Bill drew what organisers said was more than a million people for the biggest street demonstration since the 1997 handover of the former British colony back to Chinese rule.

March organisers have urged people to take to the streets again on Sunday, and protesters applied for a permit to gather next Monday, when the Legislative Council may re-convene to discuss the Bill.

Meanwhile, diplomatic pressure on Hong Kong mounted.

In the United States, senior congressional lawmakers from both parties responded to the crisis on Thursday by introducing legislation that would require the US government to provide an annual justification for the continuation of special business and trade privileges afforded to Hong Kong.

Hong Kong was returned to Chinese rule in 1997 under an agreement that promised a high degree of autonomy for the city within a "one country, two systems" framework. Critics say Beijing has been slowly undermining that deal and encroaching on Hong Kong's freedoms.

Beijing has rejected those accusations and Chinese state media said this week that "foreign forces" were trying to damage China by creating chaos over the Bill.

The hawkish Chinese newspaper the Global Times on Friday lambasted foreign leaders for being hypocrites and failing to condemn what it called "violent demonstrators".

"This is a stark provocation. These US senators make us see the dark mind of the US political elite who just want to turn Hong Kong into a chaotic place by hyping the uncontrolled violent street politics," an editorial on the newspaper's website said.