French President Emmanuel Macron and German leader Angela Merkel said Friday following a meeting of the European Council that UK Prime Minister Theresa May had shared "proof" of Russia's involvement in the assassination attempt against former Russian spy Sergei Skripal and his daughter, the two leaders said during a joint press conference in Brussels on the sidelines of a meeting of the European Council.

But although the evidence was purportedly convincing - and all three leaders are in agreement that Russia was the only reasonable culprit, and that they would help support an investigation into the matter - the EC opted not to take any immediate action against Moscow, TASS reported.

In a statement, the EC said it "agrees with the United Kingdom government's assessment that it is highly likely that the Russian Federation is responsible and that there is no plausible alternative explanation."

"The European Council condemns in the strongest possible terms the recent attack in Salisbury, expresses its deepest sympathies to all whose lives have been threatened and lends its support to the ongoing investigation."

"The use of chemical weapons, including the use of any toxic chemicals as weapons under any circumstances, is completely unacceptable, must be systematically and rigorously condemned and constitutes a security threat to us all. Member States will coordinate on the consequences to be drawn in the light of the answers provided by the Russian authorities. The European Union will remain closely focused on this issue and its implications," the document said.

As a sop to the Russia hawks, the gathering of EU leaders agreed to bolster cooperation with NATO to strengthen its resilience to chemical, biological, radiological and nuclear-related risks, and hybrid threats, including in the areas of cyber, strategic communication and counter-intelligence.

The European Council invited the European Commission and the High Representative to take this work forward and report on progress by the June European Council.

After arriving Thursday in Brussels, May told reporters and her fellow European leaders "it is clear that the Russian threat does not respect borders and indeed the incident is Salisbury was part of a pattern of Russian aggression against Europe and its near neighbors from the western Balkans to the Near East."

During a joint press conference, Merkel and Macron said they'd been given evidence by the UK to support its claims. Merkel said the reports were "well grounded," RT reported.

"[UK Prime Minister] Theresa May has provided us with some results [of the investigation]," German Chancellor Angela Merkel said at the joint press conference with French President Emmanuel Macron in Brussels on Friday. She added that the two countries will follow the British probe into the poisoning of the former Russia-UK double agent "closely" and are "convinced" that the conclusions that were made by the investigators so far are "already well-grounded."

Meanwhile, Macron said "there is no… plausible explanation" to the Salisbury incident other than Russia being behind the attack. He added that "all EU member states agree" on that allegation.

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During a separate meeting earlier this week, EU foreign ministers expressed solidarity with the UK, but also declined to take any further action against Moscow - although there was disagreement between nations.

German foreign minister called Russia "a difficult partner" but also noted that "dialogue" with Moscow ought to continue. London and Moscow should sift through the evidence "bilaterally" Maas said.  Austrian Foreign Minister Karin Kneissl argued the accusations against Russia were premature, and refused to back London, per  Strategic Culture.

Spain’s Alfonso Dastis stressed the need for more evidence before reaching conclusions. He believes the EU should wait until the OPCW conducts a thorough examination of all elements involved.

At the same time, representatives from Warsaw - who have recently proven eager to attack Moscow given even the thinnest of pretexts - expressed solidarity with London.

Skripal, 66, and his 33-year-old daughter have been in critical condition since the March 4 attack, when they were found unconscious on a bench outside a shopping center in Salisbury. Skripal had worked as a double agent for the UK intelligence agency MI6 and was jailed in Russia in 2006 for spying for Britain. He was later freed as part of a spy swap in which Russia released four spies in exchange for 10 Russian agents.

Russia has repeatedly denied its involvement and rejected UK demands to issue an explanation for how the Soviet-era nerve agent - known as Novichok - made its way to London.

However, the EU did agree to withdraw its ambassador to Moscow, saying the envoy will return to Brussels "for consultations" as several member states ponder whether to follow the UK's lead and expel their diplomats. The UK expelled 23 Russian diplomats in response to the attack, prompting a proportional response from Moscow.

Ireland, Denmark, Lithuania and the Czech Republic are also considering further measures, including the expulsion of diplomats, CNN reported.