"Convenors of such illegal gatherings will be charged for contravention of the Covid-19 Disaster Management Lockdown Regulations," Mawela further warned.
News24 previously reported that Tshwane House was damaged during a protest by South African Municipal Workers' Union (Samwu) members.
Tshwane head administrator Mpho Nawa said the special Local Labour Forum (LLF) had held a meeting with administrators and representatives of Samwu and the Independent Municipal and Allied Trade Union (Imatu) to decide on the implementation of the 6.25% annual wage increase and the benchmarking collective agreement.
A decision on the matter was not taken, as Samwu leadership allegedly walked out of the meeting, leading to a lack of quorum and causing it to collapse.
"As we continue with our negotiations with union leadership, we call upon all employees to have a full appreciation of the financial challenges the City finds itself in. As administrators, we want to see our employees happy, employed and avoid future retrenchments," Nawa said.
"Thus, our position to honour a 6.25% wage increment remains on the table and we have not reneged on this commitment that we have communicated to union leadership."
The three suspects are expected to appear in the Pretoria Magistrate's Court on Thursday.