Pensioners and students gather for Hong Kong protest

Secondary-school students and retirees joined forces at a protest in Hong Kong on Saturday, the first of several rallies planned across the China-ruled city a day after police withdrew from a university that had been rocked by a two-week siege.

Police in neighbouring Guangzhou city have arrested a Belizean citizen for allegedly meddling in Hong Kong affairs, the local Communist party newspaper said.

Lee Henley Hu Xiang, a Belizean businessman who lives in China, had funded "hostile forces" in the United States and supported activities that led to chaos in Hong Kong, the Southern Daily said. Authorities in Guangzhou were not immediately available for comment.

After more than five months of increasingly violent demonstrations, Hong Kong has seen relative calm since local elections last week delivered an overwhelming victory to pro-democracy candidates.

Despite the calm, demonstrators are pressing to keep up the momentum of their movement. They are incensed by what they see as Chinese interference in freedoms promised when Britain returned Hong Kong to Beijing in 1997.

China denies interfering and says it is committed to the "one country, two systems" formula put in place at that time. It has blamed foreign forces for fomenting unrest.

"I came out for the peaceful protest in June when there were more than one 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.

She brought her own plastic stool to a cross-generational protest at the city's Chater Garden, where a modest crowd of a few hundred people gathered to listen to pro-democracy speakers. She came with her daughter and son-in-law.

"I have seen so much police brutality and unlawful arrests. This is not the Hong Kong I know. I came today because I want the government to know that we are not happy with what they have done to our generation."

At one point the crowd rose to sing "Glory to Hong Kong", which has become the unofficial anthem of protests. Many of them put their hands in the air with five fingers outstretched, a symbol of the pro-democracy movement.

"My mum asked me to come and protect her. So I came with my husband. It has been quiet after the district elections and that is unexpected," Ponn's 26-year-old daughter told Reuters.

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

Police withdrew on Friday from the campus of Hong Kong Polytechnic University after it had been trashed by weeks of clashes between protesters and security forces.

Activists got a boost after winning backing from US President Donald Trump this week, something that has renewed global attention on the crisis in the Asian financial hub and infuriated Beijing.

"Today is an interesting ensemble because it is secondary students and elderly people. A lot of elderly people want to be heard by the police," said Lukas, a 16-year-old who was dressed in black.

"It is also a good chance for us to talk to some elderly people about how we need to stand together and fight against the Hong Kong police."