Geneva: Sarin is a powerful neurotoxin developed by Nazi scientists in the 1930s.

Originally developed as a pesticide, sarin was used to deadly effect in air raids in 1988 by former Iraqi president Saddam Hussein’s forces on the Kurdish village of Halabja in northern Iraq that left an estimated 5,000 people dead, mostly women and children. It is regarded as the worst ever gas attack targeting civilians.

A Japanese cult also used sarin in two attacks in the 1990s.

The gas works by being inhaled or absorbed through the skin and kills by crippling the nervous system.

Symptoms include nausea and violent headaches, blurred or tunnel vision, drooling, muscular convulsions, respiratory arrest, loss of consciousness and then death, according to the US Centres for Disease Control and Prevention.

Even a tiny dose of sarin — which, like other nerve gases such as soman, tabun and VX, is odourless, colourless and tasteless — can be deadly if it enters the respiratory system, or if a drop comes into contact with the skin.