aggressive and desperate, a growing fear is that it could use chemical weapons. ukraine's leader today added his voice to those warning of that danger. translation: what else have you prepared for us? - where will you strike with your chemical weapons? at the maternity hospital in mariupol? at the church in kharkiv? or at the children's hospital? so, what are chemical weapons? they release a toxin or poison, often a gas, and were used to devastating effect in the syrian conflict by russia's ally, the assad regime. and russia itself used a nerve agent, a type of chemical weapon, in salisbury in the uk four years ago. so, what is russia saying? one concern is that moscow has been making claims that ukraine has its own weapons programmes. russia actually called a un meeting today amid claims of a secret us—backed biological weapons lab, something washington and ukraine deny. russia asked the security council for today's meeting for the sole