Climate activists accuse Melbourne police of heavy-handed tactics in dealing with a protest outside the International Mining and Resources Conference (IMARC) at the Melbourne Convention Center.

The demonstrators from a coalition of eleven environmental groups sought to shut down the convention by blocking the entrances.  Around 50 people have been arrested and four were injured and taken to hospital.  One of them was a 23-year old female protester from Chile who was hurt when a police horse backed into her.

"I was standing beside her, one of the police officers had sprayed me, then threw her back away from me, and then the horse reared up and stepped on both of her legs," said a fellow protesters identified as "Paul".  "Both legs have been broken, definitely - she's got no feeling in her legs, she can't move her toes."

Victoria Police Acting Commander Tim Tully said four officers were injured.  "We've shown a hell of a lot of discretion, a hell of lot of tolerance," Tully said, claiming that the police response was "appropriate" and "in line with training".

But a number of videos posted to social media had disturbing scenes of officers striking unarmed protesters from behind with clubs, spraying protesters with pepper spray, or pushing and shoving protesters.

"We're the non-violent ones," said Emily Black of Emma Black, a spokeswoman for the Blockade IMARC alliance, accusing police of employing "some incredibly aggressive and intimidating tactics".  She added, "The police have been incredibly violent this morning."