Thousands of pro-gun activists – many openly armed, some with assault rifles – have gathered in freezing weather in the capital of the US state of Virginia for an annual demonstration in support of their right to keep and bear firearms.

This year’s rally in Richmond drew up to 50,000 people, a much larger crowd than normal after the state’s ruling Democrats – who gained control of Virginia’s legislature in the last election – said they would move to restrict gun laws.

Many angry gun-rights activists travelled from other US states to attend Monday’s rally.

The state government also feared far-right groups might use the annual Lobby Day rally to raise their profile, heightening concerns of possible violence.

But there was no visible presence of white supremacy groups.

Anti-government militia groups did attend, some of them heavily armed and masked, but took part without incident.

Further minimising the potential for clashes, left-wing groups and others in favour of gun control largely cancelled their counter-protests amid worries about their safety, though some campaigners were inside the state capital building meeting politicians.

US President Donald Trump tweeted in apparent support of the rally, saying: “The Democrat Party in the Great Commonwealth of Virginia are working hard to take away your 2nd Amendment rights. This is just the beginning. Don’t let it happen, VOTE REPUBLICAN in 2020!”

Among the many thousands who attended were staunch supporters of the President, some carrying signs that read: “God, Guns, Trump.”

Governor Ralph Northam, a Democrat, declared a state of emergency, citing concerns about possible violence.

That allowed him to ban firearms from the Capitol Square, where the rally was held. Just outside the square, however, there were plenty of gun-toting demonstrators.

“No one wants another incident like the one we saw in Charlottesville in 2017,” Mr Northam said.

He was referring to the Unite the Right rally held by extremists in Virginia, where a left-wing counter-protester was killed by a member of the far-right.

There was extensive chatter on far-right online forums ahead of Monday’s event, which occurs on Martin Luther King Jr Day, a holiday marking the legacy of the black civil rights leader.

Lobby Day is a yearly tradition in Virginia, allowing constituents to meet with state legislators on any number of issues.

Pro-gun protesters are angered by proposals to limit the number of firearm purchases per month and to impose tougher background checks.

Democrats also want “red flag” laws, which would allow authorities to quickly seize guns from people deemed potentially dangerous. But their opponents say any such move should be done only with a court order, a process that would take longer.

Mr Northam has made gun control a top priority of his administration and said he hoped to pass all three measures.

However, some local communities have declared themselves “2nd Amendment sanctuaries” and threatened not to obey the new laws.

Virginian Republican John McGuire, who is also hoping to win a seat in Congress, voiced his support for the protest.

“Our country was founded on common sense,” he said.

“Our founding fathers believed it was God-given right to protect yourself, your family and your children. That’s why these people are here today and I support them.”

-with AAP