A Hong Kong pro-democracy activist who was allegedly beaten by police in an attack captured by television cameras and beamed around the world was found guilty Thursday of assaulting and resisting police officers.

Political activist Ken Tsang was accused of splashing liquid on police officers during mass street rallies in 2014 -- the same night as he was brutally beaten in the corner of a park.

Protesters outside the courthouse said the verdict amounted to "political persecution," while Tsang's lawyer Robert Pang said the attack his client had been subjected to was much more serious than the one he had been charged for.

Tsang, 40, a member of the pro-democracy Civic Party, denied the charges but was found guilty of one count of assault and two counts of resisting police officers, which could carry up to two years in jail.

"The evidence showed that the defendant did indeed pour liquid, and that liquid fell on police officers," magistrate Peter Law told the Kowloon City courthouse.

"Although he did not have a specific target, he clearly knew there were many officers below," he said, adding that it showed "hostility."

Tsang, wearing a dark suit, sat calmly in the courtroom -- which was packed with both journalists and his supporters -- as the verdict was delivered.

He was given bail until his sentencing on May 30.

The police who allegedly beat him, who are not the same officers Tsang is accused of assaulting, are to stand trial separately.

It is the first conviction for a high profile case surrounding the rallies which blocked major highways in the city for over two months and was dubbed the "Umbrella Revolution", with protesters calling for a free vote on the city's leader.

Nearly 1,000 people were arrested in connection to the rallies including student pro-democracy leader Joshua Wong, who faces two verdicts in June for protests in 2014.

- 'He was tortured' -

Speaking after the verdict, Tsang's lawyer Pang described the "disproportionate violence" police allegedly used in the attack on the activist.

"His body was covered in wounds... he was tortured. He was punched and kicked in a dark corner as a punishment," Pang said.

Video footage aired by local television network TVB at the time showed a group of men hauling a handcuffed Tsang to a dark corner in a public park in the early hours of October 15, 2014.

One man stood over him and punched him, as three others were seen repeatedly kicking him.

Seven policemen will stand trial for the assault on the activist later this year. They have pleaded not guilty to the charges.

Tsang said he was "disappointed" about the court's decision and thanked supporters, adding that he was mulling over an appeal.

He earlier said that police brought assault charges against him to distract from the case against them.

The two incidents took place at the height of mass protests seeking free leadership elections in Hong Kong, and rocked the reputation of the city's police force.

It took a year for charges to be brought against both Tsang and the officers accused of beating him, a delay that further increased controversy surrounding the cases.

Thousands of protesters blocked major thoroughfares in Hong Kong in 2014 but ultimately failed to win any concessions from either Beijing or the city authorities.