Protests in Melbourne are turning violent for a second day, with footage posted to social media showing police appearing to use aggressive force to shove a journalist covering the blockade.

Climate change protesters have been demonstrating outside a global mining conference since Tuesday, and are expected to continue until the end of the week.

Police have been criticised for using heavy force to disperse protesters, including pepper spray and police horses.

Footage posted to Twitter shows Channel 7 journalist Paul Dowsley, microphone in hand, being forcefully pushed by police as he attempted to cover the protest. Several officers grab his clothes and shove him around, as he attempts to move to an area where media are filming the mass of people.

“Do you mind? I’m walking here,” Dowsley can be heard saying, while other people yell, “He’s a journalist”.

Victoria Police defending the actions of its officers, saying it was an “appropriate amount of force” to remove a reporter from the area, but Dowsley said he was stunned.

“I was obeying their direction to move to another area,” Dowsley said on Twitter. “I’m stunned.”

The statement from police admonished media and members of the public for “not following instructions”, saying it had “given media repeated advice to be mindful of their surroundings to ensure their safety”.

“In this case, the reporter involved did not follow police instructions to move away from the area,” police said.

In another incident at the same protest, student journalist Ailish Hallinan, who claimed she was “peacefully observing” the blockade, claimed she was pepper sprayed by police, posting photos of her reddened face to Twitter.

Media union the MEAA condemned the actions of police, saying “journalists should be free to report on protests and demonstrations without being assaulted while they carry out their duties”.

About 70 protesters gathered outside the International Mining and Resources Conference (IMARC) this morning, with police confirming 12 people had been arrested. The majority were charged with intentionally obstructing an emergency services worker.

Some protesters had glued themselves to the road at the car park entrance to the conference.

Both Victorian premier Daniel Andrews and opposition leader Michael O’Brien have condemned the protests. Andrews said there was “a big difference” between peaceful protest and the ones this week, while O’Brien called the climate protesters “ferals”.

Yesterday, shocking footage emerged of mounted police using horses to break up a chain link of protesters.

In another incident on Tuesday, protester Nicholas McCallum told Nine he was hit between the shoulder blades with a police baton while shielding a woman from being hit.

“My spine is very, very sore today,” he told Nine. “The very top of my spine in between the shoulder blades is where he connected.”

Police are expected to address media about their response to the protests later today.