Ukraine asked the global chemical weapons watchdog in The Hague on Tuesday to investigate the alleged use of banned toxic munitions by Russia against its forces.

Ukraine submitted its request after Dutch and German intelligence services said on July 4 that they had evidence of Russia’s wide-scale use of illegal chemical weapons along the front line. OPCW head Fernando Arias said the organization would intensify its monitoring efforts in relation to the Russo–Ukrainian war.

Two Dutch intelligence agencies say that Russia is increasing its use of prohibited chemical weapons in Ukraine including the World War I-era poison gas chloropicrin.