The United States military is still researching a controversial microwave weapon that could be deployed against crowds from aircraft.

The US military is to increase funding for the Active Denial System (ADS) from $2mil to $10mil despite the controversy surrounding the weapon. The ADS is described by the Pentagon as a 'non-lethal weapon' and is intended to be used a crowd control device.

The ADS works by using microwaves to heat the skin, in theory without burning it, to produce a sensation that causes crowds to flee. However, a Dortmund University researcher, Jurgen Altmann, found that microwave beams cause serious burns at levels marginally above those required to repel crowds.

The ADS was first revealed in 2001, but its controversial nature has meant it has not yet been employed in crowd control situations. 2007 tests resulted in a US soldier being hospitalised with severe burns.

It is believed that the US military intention is to develop the technology so that it can be used on crowds from aircraft above. With political and economic unrest in many countries, the development of novel weapons against crowds is of particular concern to many activists. A weapon of this nature could be employed against picket lines and factory occupations, particularly given the history of repression by various states on political protestors, trade unionists and recently, the G20 protests in London.