Hong Kong civil servants who support the protests which have rocked the city for more than five months will “burn with the rioters” according to a commentary in yesterday’s People’s Daily, the Chinese Communist Party mouthpiece.

“There is no middle ground on the issue of fighting against riots and unrest in Hong Kong … No matter whether they have given silent approval out of sympathy or connived to give support, there will be only one end to those civil servants who join the ‘black terror’. They will lose their careers and future,” the newspaper warned.

The harsh commentary described the behaviour of some Hong Kong institutions and civil servants as “surprisingly disappointing” and quoted the recent arrest of an assistant clerical officer from the Chief Secretary for Administration’s office as an example.

The article followed last week’s statement from Beijing, after a closed-door meeting the party’s elite, that the mainland would “enhance the system and mechanism over the appointment of the chief executive and principal officials”.

In a follow-up news conference, Shen Chunyao, head of the National People’s Congress committee overseeing the Basic Law, said the most direct way for Beijing to exercise authority over Hong Kong and Macau concerned the appointment of principal officials and the interpretation of the Basic Law, the city’s mini-constitution.

The People’s Daily commentary also condemned an initial decision, later revoked, by the Lands Department to require mainland banks in the city to remove protective shutters installed after attacks on their branches.

Protesters have taken aim at Chinese banks and businesses which back Beijing in recent weeks, with protesters accusing the mainland of infringing on the freedoms guaranteed when Hong Kong was returned to China in 1997.

“Some departments or public institutions of the Special Administrative Region’s government have made unprincipled concessions to recent illegal demonstrations,” it said.

“At the critical juncture of curbing violence and stopping the chaos, we see some public officials have tried to obstruct the effort, some spreading pro-violence messages on social media and some even joining the rioters. Some are even serving in high positions of the SAR government’s sensitive departments and disciplined services.

“How can they continue with this misconduct while still enjoying high pay?”

Meanwhile, Beijing’s state-run media also strongly condemned a petrol bomb attack by protesters on the Xinhua News Agency office in the city on Saturday.

It was the first time Xinhua, one of the mainland’s key symbols of its presence in Hong Kong, was targeted in the festering social unrest which has entered its 22nd week with no solution in sight.

A statement by Xinhua expressed “great indignation at the barbaric acts of the mob” and strongly condemned the attack, with the hope that the Hong Kong police would seriously investigate the incident.

In a separate commentary today, People’s Daily described the petrol bomb attack on Xinhua’s Hong Kong office as a “serious provocation against the bottom line of civilised society, and a challenge to public order”.

“Such violent crimes shall not be tolerated by any country in the world. It is not only a wilful violation of Hong Kong’s laws guaranteeing freedom of the press, but also a malicious attack on the patriotic sentiments of Hong Kong compatriots. It must be severely punished by the law.”