An ear-splitting sonic cannon used by the US army as a crowd control device in Iraq is set to be deployed at the London Olympics.

The American-built long-range acoustic device (LRAD) can be used as both loud speaker and to emit a directional beam of sound at a reportedly pain-inducing 150 decibels.

They were last unleashed on the public by police at the G20 protests in 2009, sparking outrage from critics who claimed they were loud enough to damage eardrums and even cause fatal aneurysms.

The Ministry of Defence has confirmed that an LRAD will be used by the armed forces to provide security during the Games. A spokesman said it would be used primarily in "loud hailer mode" to warn any boats on the River Thames causing concern.

"As part of the military contribution to the police-led security effort to ensure a safe and secure Games, a broad range of assets and equipment is being used by our armed forces," the MoD spokesman said.

The LRADs have been used by the US military against both Somali pirates and Iraqi insurgents.

Robert Putnam from American Technology Corporation (ATCO), which makes the devices, said: "If you stand right next to it for several minutes, you could have hearing damage."

* Olympic officials feared a computer meltdown yesterday when the first of almost a million new tickets went on sale to people left disappointed by last year's ballot. But there were of only minor glitches as seats were snapped up for events including the 100m finals. More than 70,000 tickets for access to the Olympic Park were also made available. Any tickets not sold will go back on general sale from 23 May.