A woman who apparently set her hand in concrete in the back of a car blocking traffic in Melbourne’s CBD has been arrested.

The woman had attached herself to the hatchback as part of the ongoing protest against the Land Forces expo in Melbourne.

The car was blocking traffic along busy King Street, near the intersection with Flinders Street, early on Friday.

The Ten Network aired footage of the vehicle being moved off the road near the Kings Way intersection south of Flinders Street at Southbank, with the woman still attached to it.

Police used an angle grinder to free her and she was then detained, along with another woman who had driven the hatchback.

It came as “significant protest activity” continued for a third day as the weapons expo at the Melbourne Convention and Exhibition Centre wound up on Friday.

The Spencer Street bridge remained blockaded with dozens of police on the scene before midday.

Protest organiser Caroline Da Silva said “there will be renewed vigour to protest because it’s the last day”.

“It’s our last chance to show these weapons companies that they’re not welcome here,” she said.

The first day of the expo on Wednesday descended into violence and chaos after wheelie bins were set alight and horse manure, food-grade acid and glass bottles were hurled at police barricades.

Riot officers returned fire on the 1500 demonstrators with rubber bullets, tear gas and flash-bang devices. There were also 42 arrests.

Scenes were more subdued on Thursday, as several hundred protesters marched towards the convention centre before dispersing.

They later regrouped outside the Bourke Street offices of defence contractors Hanwha Defence and Elbit Systems to oppose deals between the companies and governments, blocking access to cars and trams.

Protesters say weapons on display inside the expo have been used on civilians in the Gaza conflict.

Police and political leaders have condemned the activists’ “disgraceful” actions and tactics, labelling them “thugs”.

On Friday morning, Victorian Premier Jacinta Allan again defended the action of the police.

“They came with the intent – some – to cause violence and that is utterly unacceptable,” she told ABC Radio Melbourne.

“This is about using a conflict overseas for some pretty base political purposes here. Let’s be clear, that is really what the intent is.

Victoria Police Commissioner Shane Patton lashed out at “hypocritical” protesters, warning the largest deployment of officers in two decades would be prepared for any event for the conference.

Patton’s denunciations did not deter protesters, with Da Silva vowing they were “here for the long haul”.

“A bit of police spray, some rubber bullets – those things are harmful – but they don’t do anything to alter our conscience,” she said.

-with AAP