Britain's foreign minister said on Monday that Russian denials of responsibility over a nerve agent attack on a former Russian double agent in England were "increasingly absurd".
Boris Johnson, who briefed fellow European Union ministers in Brussels on Monday, also won renewed support from the bloc, though diplomats cautioned there was no immediate prospect of fresh economic sanctions on Russia.
"The Russian denial is increasingly absurd," Johnson told reporters as he arrived for the regular monthly meeting, which came a day after Vladimir Putin was re-elected for another six-year term as Russia's president.
"This is a classic Russian strategy ... They're not fooling anybody anymore," Johnson said.
"There is scarcely a country around the table here in Brussels that has not been affected in recent years by some kind of malign or disruptive Russian behaviour."
Russia denies any involvement in the attempted murder of Sergei Skripal and his daughter Yulia, in what was the first known offensive use of nerve gas in Europe since World War Two.
Moscow on Saturday announced the expulsion of 23 British diplomats in tat response to Britain's decision last week to expel the same number of Russian diplomats from London.
On Sunday, Johnson accused Russia of stockpiling the deadly Soviet-era nerve agent Novichok used to poison the Skripals, a charge Moscow denies. They were found unconscious on a bench in the English city of Salisbury on March 4 and remain in a critical condition in hospital.
"Ridiculous" Russian claim
On arrival at the Brussels meeting on Monday, Germany's new foreign minister, Heiko Maas, expressed his support for Britain. Later, all 28 EU foreign ministers issued a joint statement on the attack, expressing "unqualified solidarity".
"The European Union takes extremely seriously the U.K. government's assessment that it is highly likely that the Russian Federation is responsible," the statement said.
Swedish Foreign Minister Margot Wallstrom rejected an allegation by the Russian Foreign Ministry that the nerve agent used in Salisbury might have come from Sweden.
"This is just ridiculous and totally unfounded," Wallstrom said. "I think they are trying to divert the real issues here."
While there is no prospect of further sanctions on Russia being agreed on Monday, British Prime Minister Theresa May will have an opportunity to present her case for any such measures at an EU summit on Thursday, or call for others to expel diplomats.
"We need to put pressure on Russia to take part in a real enquiry about the attack," Belgian Foreign Minister Didier Reynders told reporters.