West Midlands police have taken the unusual decision of releasing video footage showing hooded looters firing shots at officers and a force helicopter during this month's riots.

It is believed to be the first evidence that police came under fire during the riots and has heightened concerns that some of the seemingly random violence and looting was conducted by organised criminal gangs.

The CCTV images show a group of between 30 and 40 young men breaking into the Barton Arms pub in the Newtown area of Birmingham on the night of Tuesday 9 August.

The group, all masked and wearing black clothing, caused extensive damage to the pub and the surrounding area, which has been plagued by shootings in recent years.

As officers arrived at the scene shortly before midnight, petrol bombs were thrown at a marked police car. It is believed as many as 11 shots were fired at the officers and a helicopter.

Eyewitnesses reported seeing a series of flashes and hearing the sound of gunshots as police approached the looters, forcing officers to take cover behind vehicles.

The force said it hoped the footage would encourage members of the public to come forward. "Releasing footage that is so disturbing in nature is an unusual step for us as a force. However, the potential for serious harm, or worse, in this incident has led us to this decision," said chief constable Chris Sims.

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

"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."

It appears that at least two weapons were used in the incident which police believe was co-ordinated by criminal gangs and involved looters, some of whom may have been as young as 13. Four spent bullet casings were found by forensic teams outside the pub. Four cartridges were also recovered at the scene.

A small amount of money was stolen from the pub, but evidence of the use of alcohol and petrol has convinced police that the looters' chief intention was to start a fire. A major investigation into arson with intent to endanger life and attempted murder has now been launched.

Detectives, forensic and ballistic experts, along with local officers, have spent the past week trawling through the CCTV footage and making house-to-house inquiries.

So far two people have been arrested for violent disorder in connection with the incident.

Siriporn Thumajaroen, who runs the Barton Arms with her husband, Wichai, was upstairs when the gang broke in. She told reporters that she could smell petrol and feared for her life. "We could have died," she told the Birmingham Mail. "Wichai put the fire out with water but we are lucky to be alive."

She added: "I have lived in this country for five years and I didn't think this kind of thing would happen here."

The shooting has revived memories of one of the most notorious incidents to blight Britain's second city in recent years. In 2005, a police officer was shot in the leg and two young men died during the race riots in the Lozells area of Birmingham, which were believed to have involved drug gangs.

"This investigation is being treated as attempted murder and arson, and I am only thankful that this is not a murder inquiry," Sims said.

"This was not only police officers' lives that were put at risk, but also members of the public who may have been passing by."

Sims said the public reaction to the appeal for information had been overwhelming. "However, I must ask once again for anyone who can help our investigation to come forward."