About 300,000 people have signed up to a group on the chat app Telegram called “IT Army of Ukraine” through which participants are assigned tasks designed to take the fight to Vladimir Putin. In so doing, they are trying to level the playing field between one of the world’s superpowers and Ukraine as it faces bombardment and invasion by Russian forces.

The sprawling hacker army has been successful in disrupting Russian web services, according to NetBlocks, a company that monitors global internet connectivity. It says the availability of the websites of the Kremlin and the Duma – Russia’s lower house of parliament – has been “intermittent” since the invasion started. The sites for state-owned media services, several banks and the energy giant Gazprom have also been targeted.