(CNN) -- Police have released dramatic security camera footage they say shows masked and hooded rioters firing shots at unarmed officers and a police helicopter in the English city of Birmingham.

They hope the public will come forward with information as they investigate the violence that took place amid widespread rioting earlier this month.

The footage shows a group of 30 to 40 young men, dressed in black, in the Newtown area of Birmingham as they attacked a pub late on Tuesday August 9, West Midlands Police said in a statement.

As police tried to disperse the group, petrol bombs were thrown at a police car and shots were fired, police said. Officers believe the rioters intended to set fire to the pub.

Chief Constable Chris Sims said the incident was being treated as attempted murder and arson.

The force has taken the "unusual step" of releasing the footage because of the potential for serious harm to his officers and members of the public, he said.

"Eleven shots were fired at unarmed officers to enable disorder to continue, whilst petrol bombs were also thrown at officers who initially attended the scene," he said.

"This footage shows seemingly co-ordinated criminal behaviour with no regard for people's lives, whether it be through the setting of a fire, shooting at unarmed officers or shooting at the police helicopter."

West Midlands Police have so far arrested more than 500 people over the disturbances in Birmingham and nearby towns, of whom more than 140 have been charged.

On Friday, Prince William and Catherine, the Duchess of Cambridge, visited areas of Birmingham affected by the disorder.

They met with residents including a small business owner whose store in central Birmingham was looted, local community leaders and emergency responders.

Among the places they visited was Winson Green, an inner-city area where three young Asian men were killed by a hit-and-run driver amid the disturbances.

Four men have been charged over their deaths and police continue to question other suspects. An eighth man was arrested Friday on suspicion of murder, police said.

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