Truckers who have blockaded downtown Ottawa for nearly three weeks have defied a growing police presence in the Canadian capital and ignored repeated warnings that they could face steep fines and possible arrest.

Officers had warned of an impending crackdown on Thursday, as busloads of police reinforcements arrived in the city and work crews took the rare step of erecting metal fences outside the senate and parliament.

Despite heavy rain, supporters flocked to Parliament Hill, while the mood of imminent confrontation receded. “I ain’t going anywhere,” said Pat King, one of protest organizers. “I haven’t overstayed my welcome. My taxes paid for me to be here.”

One of the leaders of the so-called “freedom convoy” was arrested as the interim police chief warned that action was “imminent”. Chris Barber was taken into custody on Thursday afternoon and was set to face criminal charges.

As snow fell heavily, police also arrested at least two other individuals. A speaker on the stage in front of parliament pleaded for protesters to “bring in the human reinforcements” amid fears that police could use the inclement weather to begin breaking up the blockade.

Earlier in the afternoon, the city’s deputy police chief said officers had planned for a number of scenarios after people ignored two formal warnings to leave the area immediately. “We want people to peacefully leave,” said Steve Bell said, adding: “But I can tell you that if they do not peacefully leave, we have plans, strategies and tactics to be able to get them to leave.” Police had established 100 checkpoints along a wide-ranging cordon around the city’s downtown.

Amid growing criticism of police tactics, the deputy police chief had declared his intention to break up the protest and take back Ottawa’s downtown “in the coming days”.

In parliament, the Canadian prime minister, Justin Trudeau, told MPs that it was “high time that these illegal and dangerous activities stop”.

“They are a threat to our economy and our relationship with trading partners,” he said. “They are a threat to public safety.”

Additional police officers from Quebec were deployed to reinforce Ottawa city police, the Ontario provincial police, and the Royal Canadian Mounted police in the city.

With heavy snow expected in the evening, police handed out a second round of written warnings – most of which were refused by the protesters or immediately thrown away.

“I’m Romanian, I lived through communism – this is a communist country!” said Christian Muntean, a trucker from Windsor, Ontario, who said he had no intention of leaving.

Other members of the so-called “freedom convoy” jeered at the officers, with some calling them “traitors” and others claiming they had no authority to move the vehicles blockading the city centre.

Despite the largest show of police numbers in weeks, the strategy for enforcement remained unclear. Police started blocking off key roads to isolate groups of protesters, but officers were often chased off by groups by demonstrators.

And despite local bylaws prohibiting the transport of fuel – used by protesters to keep heaters and truck engines running – officers continued to turn a blind eye as activists towed wagons of fuel towards the protest camp.

Ottawa is the convoy’s last stronghold after weeks of demonstrations and blockades that have spawned a national crisis, shuttering key border crossings and halting hundreds of millions in trade. The protests, which have increasingly large support from prominent US conservatives, have inspired similar convoys in France, New Zealand and the Netherlands.

Late on Wednesday prominent organizers had appeared to recognise the occupation was nearing its end. One organizer, Tamara Lich, tearfully told supporters she expected to be arrested by police. But leaders also attempted to rally the protesters for a final showdown.

“It’s going down,” said King in a Facebook video early Thursday morning. “Truckers, get up. Get on your radios. Get on your horns. One long blast. Let’s go, guys.”

The warnings from police came days after Trudeau invoked Canada’s Emergencies Act, empowering law enforcement authorities to declare the blockades illegal, tow away trucks and punish the drivers by arresting them, freezing their bank accounts and suspending their licenses.

Addressing a handful of supporters gathered outside parliament, King claimed that Trudeau’s actions were “unlawful” and that they did not need to comply with police orders to leave.

Since late January, protesters in trucks, tractors and motor homes have jammed the streets of Ottawa and obstructed border crossings. The demonstrations initially focused on Canada’s vaccine requirement for truckers entering the country but soon morphed into a broad attack on Covid-19 restrictions and Trudeau’s government.

The protesters are a tiny minority in a country which has, on the whole, embraced the protection against Covid offered by science. Canada has one of the highest rates of full vaccination anywhere in the world, with more than 80% of people covered.

The protests around the country have drawn support from rightwing extremists and military veterans, and authorities hesitated for weeks to move against them – in part out of fear of violence.

But Ottawa police have come under intense criticism for the cautious approach – and for failing to prevent or disperse the occupation.

The force’s commander resigned on Monday, but Ottawa mayor Jim Watson has also come under pressure. Frustration erupted at a chaotic city council meeting on Wednesday night amid tears and recriminations over the handling of the crisis.

“Mayor Watson, I have lost all confidence in you as mayor of the city of Ottawa,” said councillor Catherine McKenney at a council meeting that descended into chaos the night before.

Councillor Anne Meehan echoed such calls, and abruptly resigned from the Ottawa Police Services Board, saying: “This city is in chaos and it doesn’t need to be.”

As of Tuesday, Ottawa officials said more than 350 vehicles remained with the blockade, down from a high of roughly 4,000.

But many of those were large trucks crammed into a handful of downtown streets, presenting a logistical challenge for police hoping to tow them out of the area. The occupation has infuriated many Ottawa residents, who have complained of being harassed, intimidated and forced to endure a constant barrage of truck horns.

At a cafe near the protests, one woman said: “ I don’t care what the police do, as long as they end this thing. I work two jobs, and when I get home all I can hear is horns. I’m sick of this. I just want it to end.”