Nato and the EU are to increase cooperation to counter Russia's "hybrid warfare", the combination of concealed military force, propaganda and cyber warfare the Kremlin has allegedly used against Ukraine.
Observers believe that the West was caught on the back foot by Russia's tactics in the wake of the overthrow of the Kremlin-backed government in Kiev last year, with Russian troops posing as irregular militias seizing Crimea, and Russian propaganda branding the pro-West government in Ukraine a "fascist junta".
"Hybrid warfare combines different types of threats, including conventional, subversion and cyber," Nato secretary-general Jens Stoltenberg said at the conclusion of a three-day meeting in Antalya, southern Turkey, in which EU member states discussed enhancing military cooperation and intelligence sharing.
He said that Nato and EU foreign policy chief Federica Mogherini had agreed to "intensify Nato-EU cooperation in countering hybrid warfare".
"We will ensure that the strategies we are developing are complementary so that we can work together quickly and effectively in case of a hybrid threat against any of our members," he told a news conference.
He said that the aim of the cooperation is "that in the event of a hybrid threat, there is clarity over who does what".
Russia has also been accused of cyber-attacks and attempts to undermine the Ukrainian economy.
Moscow denies involvement in east Ukraine, where pro-Russian militias are battling Ukrainian forces.
With Kremlin propaganda targeting ethnically Russian populations in former Soviet Baltic states, the EU is to counter with its own information campaign.
"We … face sophisticated disinformation and radicalization campaigns. Our best weapon against disinformation is information based on our values of democracy, freedom of speech and open societies," Stoltenberg said.
Mogherini said that while the challenges faced by Nato and the EU differed, "What is extremely important for us is a strong coordination ... in particular when it comes to information sharing, when it comes to the new kind of threats we are facing all around us".
She added: "This does not necessarily mean a military approach. But we cannot rule out a military aspect of our work."
The announcements come with the EU requiring Russia to refrain from employing its UN Security Council veto, in order to secure a resolution authorising military force to target people smugglers in Libya.
German foreign minister Frank-Walter Steinmeier expressed optimism on Thursday that Russia would support the resolution.