The Virginia governor on Wednesday said he was temporarily banning all guns and weapons from the area around the Capitol in Richmond ahead of a major gun rights demonstration set for next week.

Ralph Northam, who is leading the push for stronger gun laws in his state, said he wants to avoid a repeat of violence that erupted at a 2017 white supremacist rally in Charlottesville, when a march by white nationalists erupted into violence and led to the death of a counter-protester.

Northam said on Twitter he had received credible intelligence from law enforcement agencies of threats of violence surrounding a lobby day against stricter gun laws planned for 20 January.

“We support citizens’ rights to peacefully protest and express their views to their elected officials. But we must also keep the public, as well as those who work around Capitol Square, safe,” Northam said.

The lobby day, organized by a Virginia gun rights group, is expected to attract tens of thousands of people to the state capital, including members of anti-government groups from other states. Northam said on Twitter that law enforcement intelligence suggested “militia groups and hate groups, some from out of state, plan to come to the Capitol to disrupt our democratic process with acts of violence”.

A “substantial number” of the demonstrators “may be armed, and have as their purpose not peaceful assembly but violence, rioting, and insurrection”, the governor’s executive order read.

A state official told the Associated Press that threatening social media posts, including a photo of an AR-15 rifle and text saying there were “great sight angles from certain buildings” near Capitol Square, had prompted the governor’s decision.

The Virginia Citizens Defense League (VCDL), the state gun rights group organizing Monday’s lobby day event, had previously asked supporters not to bring rifles and other long guns to the lobby day, citing concerns about the optics of gun owners toting AR-15s or AK-47s around the state Capitol. But the group had publicly anticipated that the event would attract “enough citizens armed with handguns to take over a modern mid-sized country”.

Philip Van Cleave, the VCDL president, told the Guardian that the group was consulting its lawyers and exploring a legal challenge to the governor’s ban on weapons in Richmond’s Capitol Square. In the meantime, he said, the group would advise supporters who wanted to be armed to stay in the area outside of the immediate Capitol grounds.

Because VCDL is expecting at least 50,000 supporters to show up to Monday’s event, and the group has been informed that the Capitol grounds will only be able to hold 10,000 people, there will probably be a large number of armed gun rights activists in the streets of downtown Richmond regardless, Van Cleave said.

Asked about the threatening social media posts officials had cited, Van Cleave said that he himself had forwarded “between five and 10” concerning posts to Virginia law enforcement, including one aerial photo of the Capitol grounds that had been marked with potential locations for a sniper, but that he was not sure if any of the posts were credible threats.

“Anybody can get an overhead shot from Google, and they can get a red pen and they can circle spots, and they might not know what they’re doing,” he said.

The group was dealing with a deluge of false and distorted information about lobby day, he said, and it wasn’t clear how much of it was coming from “some keyboard warrior”.

Asked how credible he thought any threats of violence related to the event might be, Van Cleave said, “I don’t know. I personally haven’t lost any sleep over it.”

Since Democrats won control of Virginia’s state government in the November elections and promised to pass a slate of stricter gun laws, pro-gun activists across the state have organized a vigorous grassroots movement to protest against the new bills. More than 125 counties, cities and towns across the state have passed “second amendment sanctuary” resolutions, pledging to respect gun owners’ rights and to not enforce any state gun laws deemed to be unconstitutional.

The local second amendment sanctuary movement has attracted hundreds and even thousands of supporters at local government meetings, drawing comparisons to the Tea Party movement. The rhetoric of some of these local activists has been intense, with calls of treason and tyranny, and open references to civil war. Lies, conspiracy theories and misinformation about Democrats’ proposed gun control bills have circulated widely, prompting outrage and threats of violence against Democratic politicians.

This grassroots gun rights movement in Virginia has attracted attention from pro-gun activists across the country, some of whom have pledged to come to Virginia to stand with local activists on Monday, Van Cleave said. He said he was expecting buses of gun supporters from as far as Texas and Connecticut, and even some activists from the west coast, including California, Washington and Oregon.

The movement has also been seized on by more extreme groups, including anti-government militias and white supremacists, who see the tensions in Virginia as a potential flashpoint that could lead to violent resistance and civil war, often referred to in online conversations as the “boogaloo”, according to an analyst at the Anti-Defamation League, which monitors extremists.

The Oath Keepers, a national organization of current and former law enforcement and military officials described by the Southern Poverty Law Center as one of the country’s largest anti-government groups, called for members to travel to Virginia to attend lobby day and said they also intended to train local activists.

A handful of the same extremists who attended the Unite the Right rally in Charlottesville, Virginia, in 2017 have also publicly suggested they might attend lobby day, the Daily Beast reported on Wednesday.

The bill that sparked the most outrage from Virginia gun owners, a proposed ban on assault weapons that originally included language that would ban the “possession” of certain military-style guns, has already been withdrawn from consideration by its sponsor, the state senate majority leader, Richard Saslaw.

Virginia Democrats have made some statements that have only increased tensions. In mid-December, Democratic congressman Donald McEachin publicly speculated that the governor might call in the national guard to enforce gun laws if local law enforcement officials refused, something that a spokeswoman for the governor said was not actually under consideration.

Gun rights activists in Virginia also pointed to Northam’s response to a question in early November about whether he supported confiscating assault weapons from citizens who already owned them. Asked directly about confiscation, Northam “demurred”, the Washington Post reported at the time.

“That’s something I’m working [on] with our secretary of public safety,” Northam was quoted as saying. “I’ll work with the gun violence activists, and we’ll work [on] that. I don’t have a definitive plan today.”

Two days later, during a National Public Radio interview, Northam was again asked if he planned to confiscate assault weapons that Virginia citizens already owned.

“No ma’am, not at this stage,” Northam said. “We’re looking at banning the sales of assault weapons ... that would be what we would start with.”

The governor’s office clarified in a statement in early December that proposed assault weapon ban legislation, which had included language banning the possession of military-style weapons, would include a “grandfather” provision, allowing citizens who currently owned the guns to keep them.