Secondary school students and retirees have joined forces to protest in Hong Kong, as pro-democracy activists vow to battle what they say are incidents of police brutality and unlawful arrests.

Key points: Despite a lull in violence, protesters have vowed to continue their activities

Despite a lull in violence, protesters have vowed to continue their activities The US Government has officially backed the pro-democracy movement

The US Government has officially backed the pro-democracy movement China has accused the US of meddling in its internal affairs

Hong Kong has seen relative calm since local elections last week delivered an overwhelming victory to pro-democracy candidates, but demonstrators appear keen to maintain the momentum of their movement.

"I came out for the peaceful protest in June when there was more than 1 million people, but the Government did not listen to our demands," said a 71-year-old woman in Hong Kong's Central district, who only gave her name as Ponn.

Protesters have vowed their movement will not fade away until there is greater democracy in the Chinese territory. ( AP: Ng Han Guan )

At one point the crowd in the park rose to sing "Glory to Hong Kong", which has become the unofficial anthem of protests.

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Many of them put their hands in the air with five fingers outstretched, a symbol of the pro-democracy movement.

Some of the young protesters waved American flags, a sign of appreciation after US President Donald Trump this week signed into law bills that back the protesters and threaten China with possible sanctions.

Hong Kong's leader, Carrie Lam, has appealed for the current calm to continue but has refused to bow to protesters' demands, which include free elections for her post and the legislature as well as an independent probe into alleged police brutality.

A top Hong Kong official said the Government was looking into setting up an independent committee to review the handling of the crisis, which has seen increasingly violent demonstrations since starting more than five months ago.

"It's still a very early stage of the revolution," a masked activist, who gave her name as Mai, 26, said.

"People are tired physically and mentally, so we are waiting for the right moment for a fightback."

Protesters this week have urged Britain and other countries to follow US footsteps in legislating laws to support its cause.

One of the new US laws prescribes sanctions on officials found guilty of human rights abuses and requires an annual review of a special trade status for Hong Kong.

The other bans the export of certain nonlethal munitions to Hong Kong police.

China has warned of strong countermeasures and Hong Kong's Government has slammed the US move as unwarranted meddling in its affairs.

More rallies are planned for Sunday, including an anti-tear gas protest and a gratitude march to the US Consulate.

Protesters raised their hand to symbolise the five demands of the pro-democracy movement. ( AP: Ng Han Guan )

A 70-year-old retiree, who gave his name as Ko, said seniors could offer guidance to the younger protesters.

"Starting from day one I have been involved in this movement and there is no reason to stop now," said Ko.

The protesters are angry over creeping Chinese interference in Hong Kong that they say is eroding their rights promised when the former British colony returned to Chinese rule in 1997.

Since the unrest broke out in June, protesters have disrupted traffic, smashed public facilities and pro-China shops and hurled petrol bombs in pitched battles with riot police who have responded with volleys of tear gas and water cannons.

The occupation of several universities by protesters earlier this month after fiery clashes with police capped one of the most violent chapters in the turmoil, which has contributed to the city's first recession in a decade.

Hong Kong police have arrested 5,890 people as a result of the protests.

"My mum asked me to come and protect her," senior citizen protester Ponn's 26-year-old daughter said.

"We should not stop there; I came today because we have to keep fighting."

Pro-democracy protesters have called on democratic powers to help Hong Kong. ( AP: Kin Cheung )

AP/Reuters