Russia's clear warning that it can easily chip away at Europe's defences

The brutality of Russia's drone assaults on Ukraine's towns and cities shows no let up.

"Savage strikes, a deliberate targeted terror" is how the Ukrainian President Volodymyr Zelenskyy described the latest overnight bombardment. Some 595 attack drones and 48 missiles were involved and even if only a small fraction made it through Ukrainian air defences, the destruction - in Sumy and Odessa, Zaporizhia and Kyiv - is significant.

Also overnight, Denmark reported yet more drone sightings. It has not named Russia directly but after a week in which unidentified drones have resulted in the temporary shutdown of military and civilian airports, it is banning all civil drone flights and describing the threat as a hybrid attack.

Germany is also raising the alarm over unexplained drone activity along its border with Denmark. Germany's interior minister said on Saturday: "We are witnessing an arms race, an arms race between drone threats and drone defences.

It is a race we cannot afford to lose." NATO is having to deploy extra assets to beef up its Baltic Sea defences and its Eastern flank. European nations are working to establish a drone wall along their borders with Russia and Ukraine.

Germany is setting up a drone defence centre to make sure it has what it needs to protect itself. The Kremlin is forcing NATO to divert assets to protect its airspace and sub-sea infrastructure at a time when Europe is trying to work out how best to support and finance Ukraine.

Read more:Putin's top diplomat issues warningWhy Trump has made a U-turn With drones an inexpensive element of its hybrid warfare arsenal, Russia is sending a clear warning that it can relatively easily chip away at Europe's defences and that Europe had better focus on protecting itself. "If NATO begins to look too rattled, that actually is encouragement for Putin precisely to step up the pressure," says Mark Galeotti, a specialist in Russian security.

"So really we need to be holding our nerve. "Yes, reserving the right to shoot things down that look like direct threats, but otherwise actually talking down, not talking up, the nature of the threat while of course we arm so that we are even more prepared." Last week, Estonia said its fighter jets had escorted three Russian MIG fighter jets out of their airspace after a 12-minute incursion, which Russia denies ever took place.

On Saturday, Estonia pledged €10m (£8.7m) to NATO's "Prioritised Ukraine Requirement List" or PURL programme, which sees US-produced weapons, paid for by NATO's European partners, fast-tracked to Ukraine. Zelenskyy posted on Sunday after speaking with the NATO secretary general that PURL is moving forward well.

And that is just what Russia is trying to prevent..