Russia is suspected of deliberately leaking chemical waste into a river, with deadly consequences for wildlife.

Ukrainian officials say the Russians deliberately poisoned the Seym River, which flows into the Desna. The Desna connects with a reservoir in the Kyiv region and a water supply used by millions.

The pollution crossed the international border just over a mile away and made its way into Ukraine’s Sumy region. The Seym’s natural ecosystem crashed. Fish, molluscs and crayfish were asphyxiated as oxygen levels fell to near zero. Settlements along the river reported mass die-offs.