The Pentagon's enthusiasm for non-lethal crowd-control weapons appears to have stepped up a gear with its decision to develop a microwave pain-infliction system that can be fired from an aircraft.

The device is an extension of its controversial Active Denial System, which uses microwaves to heat the surface of the skin, creating a painful sensation without burning that strongly motivates the target to flee. The ADS was unveiled in 2001, but it has not been deployed owing to legal issues and safety fears.

Nevertheless, the Pentagon's Joint Non-Lethal Weapons Directorate (JNLWD) in Quantico, Virginia, has now called for it to be upgraded. The US air force, whose radar technology the ADS is based on, is increasing its annual funding of the system from $2 million to $10 million.

Previously.