ROME — The naval skirmish in the Sea of Azov marks a new phase in the festering conflict between Ukraine and Russia.

Europe should be on high alert. Beyond exacerbating deep tensions between Kiev and Moscow, the escalation — which saw Russia seize three vessels in international waters, detain 24 Ukrainian sailors and block commercial shipping in the Kerch Strait, which connects the Azov Sea to the Black Sea — also risks kneecapping Ukraine’s resilience as an independent country and diverting it from its troubled path to democracy.

Perhaps most importantly, the clash highlights the failure of Europe’s sanctions regime against Moscow as an effective tool for keeping Russian President Vladimir Putin in check. The EU urgently needs to radically rethink the way it handles Russia.

The motives behind the Kremlin’s operation are not mysterious. Moscow is seeking to reinforce its position in the Azov Sea and limit Kiev’s access to Ukraine’s eastern ports. In doing so, the Kremlin appears to be pursuing a similar strategy to what it did in Georgia, where its creeping annexation also took the form of constantly changing “borders” between Georgia and South Ossetia.

Intervening violently in Ukraine also shifts the Russian public’s focus away from domestic politics and back to the war in the east, at a time when Putin's popularity has dropped to its lowest point since the 2014 annexation of Crimea, following a controversial pension reform. Today, some 58 percent of Russians say they support Putin, down from a 75 percent high last year, according to a recent Levada Centre survey published in October.

What this latest skirmish suggests is that the approach Europe has taken regarding sanctions is no longer sufficient to contain Russia and prevent escalation in Ukraine.

Moscow’s move prompted Ukrainian President Petro Poroshenko to call for martial law to be established. In the Ukrainian parliament, that measure was watered down to a 30-day martial in certain regions. MPs also voted to ensure parliamentary elections scheduled for 2019 will go ahead.

The chaotic response in Ukraine gave ammunition to those who — like Putin himself — accuse Poroshenko of seeking to extend his power by cancelling elections, to hold on to power despite a steep decline in popularity.

Russia has also deployed missiles to Crimea, making it clear Moscow won’t back down when it comes to protecting what it considers to be part of Russia.

The EU and NATO responded to the incident quickly and effectively, calling on Moscow to reopen the Kerch Strait, deescalate, adhere to international law and ensure freedom of navigation. But that is far from enough.

Above all the speculation about who provoked whom, and who will use this incident for what political purpose, one thing is clear: The EU must rethink its sanctions policy toward Russia.

The EU imposed sanctions on Russia in 2014, following its annexation of Crimea, and it has renewed them every six months. The basis for keeping sanctions in place was the ongoing conflict in Ukraine and, more specifically, the non-implementation of the Minsk accord between Ukraine, Russia, France, and Germany intended to help bring the war to an end.

Starting in 2016, the EU added another strand to its Russia strategy: selective engagement on issues of common interest. This two-pronged strategy had the double merit of securing political unity — to Moscow’s surprise — among EU member countries, while also arguably preventing the conflict from escalating further.

The situation in the Sea of Azov suggests that although EU leaders are likely to maintain their united support for sanctions, the current sanctions policy is no longer able to contain the conflict.

When EU leaders meet to greenlight sanctions renewal at December’s European Council summit, Putin’s moves in the Kerch Strait will mean even the most Moscow-friendly EU governments — in Rome, Athens and Budapest — are likely to be reluctant to stick their necks out for the Kremlin.

This political unity will not be a response to violations of the Minsk agreement. It’s become crystal clear over the past few years, in fact, that the Minsk agreement will not be fully implemented. Neither Moscow nor Kiev is likely to budge first in fulfilling their side of the deal. They don’t see the point.

EU leaders have renewed sanctions every six months. The official reason for doing so has remained unchanged — it’s about Minsk — but the real motivation has always been something more pressing: the poisoning of ex-spy Sergei Skripal in the U.K. the last time around, and now this latest naval dispute.

What this latest skirmish suggests is that the approach Europe has taken regarding sanctions is no longer sufficient to contain Russia and prevent escalation in Ukraine.

That suggests a different path to be taken. Instead of tying the decision to Minsk or other forms of negotiations, the EU should spell out a clearer set of criteria: one based on violation of international law and human rights.

This approach, championed most prominently by the Netherlands, would add clarity to the EU’s approach vis-à-vis Russia and strengthen its impact.

It would send a signal to Moscow about how it is expected to behave — and make clear that the EU is ready to toughen its response if necessary.

Nona Mikhelidze is head of the Eastern Europe and Eurasian program at Istituto Affari Internazionali. Nathalie Tocci is director of Istituto Affair Internazionali and special adviser to European High Commissioner for Foreign Affairs Federica Mogherini.