Police planned to disperse the crowd at a Sydney protest against the visiting Israeli president, Isaac Herzog, if it exceeded 6,000 people, according to correspondence between senior New South Wales public servants.

The messages released under freedom of information (FoI) laws contain information not referenced in public comments by the NSW premier, Chris Minns, and the police commissioner, Mal Lanyon.

They have said police only moved to disperse the demonstrators at Sydney’s town hall after they sought to march in defiance of “major events” and public assembly restrictions.

Several pro-Palestine protesters have been charged with public order offences after the violent clashes between police and demonstrators on 9 February.

The independent police watchdog, the Law Enforcement Conduct Commission (Lecc), is investigating alleged police brutality. Several protesters have said they will launch civil claims against NSW police.

In messages from the night on the encrypted messaging app Signal, the secretary of the NSW premier’s department, Simon Draper, wrote to the deputy secretary, Kate Meagher, at 5.42pm.

“What’s the view from POC Kate Meagher? Numbers? Static?” Draper wrote, according to the chat released under FoI laws.

“Static for now, but there are some speakers urging marching. At least 3-4K,” Meagher replies. “Police will be dispersing them if numbers exceed capacity. Crowd sentiment is reportedly calm. Lots of mums and dads.”

Asked by another senior public servant what the capacity for the event was, Meagher wrote back at 6.20pm: “Likely 6K at TH [town hall].”

She was working from inside the NSW police operation centre (POC) during the protest.

“Good news they think people have stopped arriving!” Meagher wrote at 6.31pm. A minute later, she wrote that police were “feeling ok that March [sic] not likely – maybe a splinter’”.

In the final messages released by the government, Meagher wrote at 7.03pm: “Ok, some marching now”, before clarifying these were “Attempts”. No messages covering the time of the clashes between police and protesters were released.

Guardian Australia has reported that some protesters at town hall began to try to march to NSW parliament at about this time. Widespread efforts by police to disperse crowds began at about 7.30pm, including arrests and the use of controversial tactics, including containment lines and pepper spray.

Several violent confrontations were captured in viral social media footage. In one incident, Muslim men who were praying were aggressively moved on by police.

Speaking at a joint press conference with Lanyon the day after the protest, Minns said police were put in an “impossible situation” after protesters attempted to march. He has maintained protest organisers were responsible for the clashes, describing them at budget estimates last month as a “pack of communists … intent on having a confrontation with police”.

Lanyon, who has apologised for the incident with the group praying, has maintained that police were “required” to start dispersing the crowd because the protesters sought to march.

In an interview on ABC radio on 12 February, he rejected the suggestion that police had coordinated efforts to move on protesters ahead of the end of a Jewish community event attended by Herzog at the nearby International Convention Centre, which concluded about 9pm.

The Sydney Morning Herald reported that attendees at the event were held in place by police for 30 minutes to avoid them meeting protesters.

NSW police did not respond to questions about any plan to move on protesters if the crowd reached 6,000 at town hall. They said Guardian Australia’s questions “relate to a current Lecc investigation”.

Estimates for the number of attendees have varied.

The Palestine Action Group unsuccessfully challenged the government’s use of “major event” powers before the protest in the NSW supreme court. Organisers told the court they expected about 5,000 people in town hall square which they estimated had a capacity of about 4,500.

The Palestine Action Group said this week it was not told by police about any plan to disperse protesters if the crowd reached 6,000.

The assistant police commissioner Peter McKenna told reporters on the night of the protest, after police had dispersed the crowd, that he estimated 6,000 people had attended.

Minns did not directly respond to a question about whether the messages by senior public servants in his department were at odds with his account of the police response.

A spokesperson for the premier said the department “coordinates agencies through the government coordination centre (GCC), which operates inside the police operations centre during all major events”.

“NSW police were operating in extraordinarily difficult circumstances,” the spokesperson said, adding it was not appropriate to comment further during the Lecc investigation.

A spokesperson for the premier’s department said the GCC was “not responsible for police operations but works to support whole-of-government efforts to address risks to public safety, traffic and transport systems issues, crowd management and communications”.