A young woman was taken to hospital after being knocked down by a police horse during a volatile blockade at an international mining conference in Melbourne. Police said four officers were injured in the melee, and 40 people were arrested.

Camila Serra, 23, was taken to the Alfred Hospital in a stable condition with a leg injury sustained today's protest at the Melbourne Convention and Exhibition Centre.

Another protester said he saw her fall backwards after being struck by a police horse. Another activist has been treated at the scene for a minor cut to his head.

An injured protester is loaded into an ambulance after sustaining an injury during a protest outside the Melbourne Exhibition and Convention Centre, Melbourne. (AAP)

Police intervene to protect an man from a mob of protesters outside the Melbourne Exhibition and Convention Centre, Melbourne, Tuesday, October 29, 2019. (AAP)

A police spokeswoman said more than 40 protesters had been arrested, with the majority of offences relating to failing to obey police direction or intentionally obstructing an emergency service worker.

"Four officers have also been injured while making arrests this morning," the spokeswoman said. "Three have been taken to hospital for injuries including a dislocated finger and minor head injuries."

Two people were arrested for animal cruelty for allegedly assaulting a police horse.

Hundreds of activists linked to numerous groups gathered outside the convention centre in an effort to stop delegates attending the International Mining and Resources Conference (IMARC).

Hundreds of climate protesters have converged on a Melbourne conference centre in a bid to stop an international mining conference from going ahead. (AAP)

More than 7000 delegates from nearly 100 countries are expected to attend the three-day conference, which kicked off on Tuesday.

Among them is Pioneer Resources chairman Craig McGown, who was seen to have a bottle of water poured over him by a protester. He was pushed during his approach to the conference and a woman shouted "shame" at him.

Another demonstrator was seen repeatedly spitting on another delegate outside the venue.

An injured Police officer is seen on the ground following an incident with protesters outside the Melbourne Exhibition and Convention Centre, Melbourne, Tuesday, October 29, 2019. (AAP)

Hundreds of climate protesters have converged on a Melbourne conference centre in a bid to stop an international mining conference from going ahead. (AAP Image/James Ross) NO ARCHIVING (AAP)

The protesters picketed at multiple entrances to the centre, chanting "land rights not mining rights, shut IMARC down" and "blood on your hands".

They say the police have been aggressive, placing one man in a headlock and pushing others as well as using capsicum spray.

"I think the police have been incredibly hostile ... I'm quite shocked by how aggressive they've been," protest organiser Emma Black told 3AW.

A statement released by conference organisers said they welcomed the protesters' right to make their views known, "but not to cause disruption" (9News)

"We condemn the violence of the police but we've come into this with the clear principle of being non violent."

"We are here to non violently and peacefully exercise our right to protest and so far all we've seen is violence from the police."

Despite initial concerns over traffic disruptions, VicRoads says traffic is flowing through nearby streets and trams are running.

The IMARC is Australia's largest annual industry event and attracts delegates from the resources, investing and technology sectors.

More than 7000 delegates from about 100 countries are attending the three-day conference and organisers say the protest action is based on misconceptions about the mining industry.

"There is a misconception that as an industry mining does not operate with sustainable principles in mind," they said in a statement.

Mining was vital for the production of electricity, solar panels, electric car batteries, pacemakers and medical apparatus and public transport, they added.

Police and protesters crush together outside the Melbourne event venue. (9News)

Police had arrested more than 20 people before 10am on Tuesday morning, as protesters hoped to shut the mining conference down. (9News)

This year the conference will consider the importance of battery minerals, used in the emerging electric car market, and the growing importance of ethical investment for resource companies.

Protesters plan to disrupt all three days of the conference and will be joined by Victorian Greens Leader Samantha Ratnam today and federal Greens MP Adam Bandt tomorrow.

Deputy Prime Minister Michael McCormack described the protests as "disgraceful, absolutely disgraceful".