Sham had been making his way to the annual general meeting of the Civil Human Rights Front, the pro-democracy group he leads, when he was attacked for the second time in the past two months. The front, which is responsible for some of the largest peaceful marches in the city, was expected to discuss a protest in Kowloon on Sunday.

Sham was conscious when sent to Kwong Wah Hospital and was understood to be in a stable condition. On Thursday morning he was seen in a wheelchair talking to his lawyer.

Writing on Facebook in the early hours of Thursday, Sham said his wounds had already been sewn up, and he expressed gratitude to his comrades, medical staff and police officers who arrived at the scene.

“I am sorry that I have made everyone worried. I will recover soon and continue to insist on our five demands and our beliefs in peaceful, rational and non-violent [protests],” Sham wrote, referring to the protesters’ calls which include an independent investigation into police actions during recent unrest and the implementation of universal suffrage.

Speaking on Thursday after visiting Sham, Eric Lai Yan-ho, the group’s deputy convenor, said Sham was stable and awake, but would have to stay in hospital for recovery and physical therapy.

“His head and joints were injured, but he has no fractures,” Lai said. “He calls for citizens in Hong Kong as well as police officers to allow a safe, lawful and peaceful rally this coming Sunday.”

Lai urged the police commissioner to issue a letter of no objection to the march.

He added that Sham had said he could not recognise the faces or the ethnicities of the assailants, after reports that they were South Asian sparked a small number of comments online against that community.

“He asked Hongkongers not to take any actions as revenge against any particular groups of ethnicities or race, because we have to focus on the system, on the violence caused by the structure and the systems in Hong Kong,” Lai said.

On Thursday afternoon police returned to the scene of the incident to find witnesses and retrieve surveillance footage.

Leaders of the Muslim community condemned the “barbaric and brutal attack” on Sham and called it an attempt to divide society.

“Our thoughts and prayers are with Mr Jimmy Sham and we pray for his health and well-being,” the Incorporated Trustees of the Islamic Community Fund of Hong Kong wrote in a statement.

“We stand together with the people of Hong Kong and shall continue to strive for maintaining an atmosphere of equality, peace and harmony.”

Pro-democracy lawmakers on Thursday were up in arms about the attack, which they described as a clear attempt to intimidate Hongkongers.

“The front is the totem in Hong Kong for peaceful protests. This very vicious attack took place practically on the eve of [Sham’s] call for yet another peaceful protest in Hong Kong on Sunday,” said Council Front lawmaker Claudia Mo Man-ching.

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“We cannot help feeling that this entire thing is part of a plan to shed blood on Hong Kong’s peaceful protests,” she said.

Lawmaker Ip Kin-yuen, representing the education sector, also suspected the attack was a move to provoke protesters to fuel further clashes with police.

“I call on Hongkongers not to fall into the trap. We should stay calm and not be provoked,” he said.

Civic Party lawmaker Tanya Chan, convenor of the pro-democracy bloc, also accused some forces of trying to fuel further chaos so the government would have an excuse to postpone the district council elections next month. City leader Carrie Lam Cheng Yuet-ngor said earlier the government remained committed to holding of the polls – in which the pro-democracy bloc is expected to enjoy the upper hand – on time.

Amnesty International called for a prompt and thorough investigation into Wednesday’s attack.

“The authorities must promptly conduct an investigation into this horrifying attack, bring all those responsible to justice and send a clear message that targeting activists will have consequences,” said Joshua Rosenzweig, head of Amnesty’s East Asia regional office.

Since August, at least nine pro-democracy figures have been attacked, including Democratic Party lawmaker Roy Kwong Chun-yu. Offices of pro-establishment politicians, meanwhile, have been trashed by radical protesters during the anti-government protests, which have run since June, when they were sparked by opposition to legislation which would have allowed extraditions to mainland China.

Additional reporting by Chris Lau