A Hong Kong court jailed a protester Thursday in the first sentence handed down over a riot that erupted in February and saw violent clashes in the city fuelled by anti-China sentiment.

The violence erupted after officials tried to clear illegal street hawkers from a busy commercial neighbourhood during Chinese new year, with police firing warning shots into the air.

Beijing officials blamed the clashes, which saw some 30 people arrested and charged with rioting, on "radical separatists".

Some participants were from "localist" groups pushing for more freedom for the semi-autonomous city or even a split from Beijing.

A magistrates' court sentenced Chan Pak-yeung, 31, an active member and online radio presenter for the localist political party Civic Passion, to nine months in prison for resisting and assaulting police, the party said.

The court had heard that Chan hurled plastic water bottles at police and had kicked officers who tried to arrest him, news reports said.

But Civic Passion questioned the evidence against Chan after the ruling.

"This must be political prosecution," said the party's vice chairman Alvin Cheng.

Cheng said he was worried that there would be more jail sentences over the riots.

Tensions are high in the city, which is ruled under a "one country, two systems" deal set up when it was handed back to China by Britain in 1997.

That agreement guarantees Hong Kong's freedoms and way of life for 50 years, but there are growing concerns that Beijing is increasing its influence.

Hong Kong saw mass pro-democracy rallies calling for fully free elections erupt in 2014, but anger built up after authorities cleared protest sites and gave no concessions over political reform.

The situation was worsened after five Hong Kong-based booksellers selling titles critical of Beijing were detained by Chinese authorities in late 2015.

As a result, some activists are now pushing for a complete break from China, with a fledgling independence movement gains support.

Police fired warning shots in the air during the February clashes, while demonstrators hurled bricks levered up from pavements, charged police lines with homemade shields and set rubbish on fire.

About 100 people were injured, including police officers, journalists and protesters, and 65 were arrested in the rare outbreak of violence.