Analysis Toxic agent evidence is growing

Gasping - choking - on Ukraine's frontline, the country's soldiers report what statistics show: a persistent use of chemical weapons, mostly teargas, whose deployment on the battlefield is illegal.

- Dan Sabbagh

The US and UK go further in their accusations, and say Russia is guilty of using another toxic agent, chloropicrin, first used in First World War trenches.

The US and UK say the Russian ministry of defence's radiological, chemical and biological defence troops, known as RKhBZ, is a specialist unit responsible in part for the use of chemicals on the battlefield, and that its head was Igor Kirillov, killed in Moscow by a bomb hidden in a scooter in an attack carried out by Kyiv.

Ukraine says 4,800 uses of chemical weapons by Russia have been documented since the start of the full-scale invasion in February 2022, and more than 2,000 people have been treated in hospital.

Media reports, citing soldiers' testimony, report that small first-person view drones are used to drop gas grenades on Ukrainian positions, choking soldiers or forcing them into the open so they can be picked off.