European Union member states have agreed at a summit in Brussels to take additional punitive measures against Russia for a nerve-agent attack in Britain.
Moscow responded by accusing the EU of joining a London-driven hate campaign against Russia.
Moscow has denied that it is behind the attack on Russian ex-spy Sergei Skripal and his daughter, the first known offensive use of a nerve toxin in Europe since World War II.
But German Chancellor Angela Merkel said evidence of Russian culpability presented at the summit on March 23 by British Prime Minister Theresa May was "very solidly based."
Merkel promised new measures after EU leaders agreed late on March 22 to recall their ambassador to Moscow.
EU envoy Markus Ederer is expected to arrive in Brussels from Moscow during the weekend, an EU statement said.
"Germany and France agree that additional steps, on top of the recall of the ambassador, are necessary," Merkel said at a joint news conference with French President Emmanuel Macron after the March 23 Brussels summit.
Macron called the attack "unprecedented" and said Europe must respond.
"It is an aggression against the security and sovereignty of an ally that is today a member of the European Union," Macron said. "It demands a reaction. This is clear."
The EU also collectively condemned the attack and declared in a joint statement that said it was "highly likely" Moscow was responsible for the poisoning of the Russian former double agent in Salisbury, England.
The Kremlin has voiced "regret" over the EU's decision to recall its envoy to Russia.
President Vladimir Putin's spokesman made the remarks on March 23, hours after EU leaders said there is "no plausible alternative explanation" than Russian responsibility for the nerve-toxin attack on Sergei Skripal and his daughter Yulia.
"We regret in this context that again such decisions are made using the wording 'highly likely' and judgments are based on this," Kremlin spokesman Dmitry Peskov told journalists.
"We don't agree with this and we repeat again that Russia absolutely definitely has nothing to do with the Skripal case," Peskov said. He said the Kremlin specifically regrets the "recall [of the envoy] for consultations."
Peskov said Russia did not know what "precise information the British side used when it discussed the topic of the Skripals with its colleagues."
"We also don't know what exactly the leaders of the EU states agreed with when they talked about their support for Britain," he said.
Russia "unfortunately is not able to receive any information at all directly on the so-called Skripal case," Peskov said.
The 66-year-old Skripal and his 33-year-old daughter have remained hospitalized in critical condition since they were found collapsed on a bench in Salisbury on March 4.
A British judge said on March 22 that they may have suffered brain damage and the prospects for recovery were uncertain.
Britain accuses Moscow of using a military-grade nerve agent that it developed during the Cold War, part of a series known as Novichok, to attack them with intent to kill.
Foreign Secretary Boris Johnson said on March 16 that it was "overwhelmingly likely" it was Putin's decision "to direct the use of a nerve agent on the streets of the U.K., on the streets of Europe for the first time since the Second World War."
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Lithuanian President Dalia Grybauskaite said she was ready to expel Russian spies from her country -- following the lead of Britain, which has kicked out 23 Russian diplomats it said were spies.
Other Baltic states, as well as Poland and the Czech Republic, said they are also considering taking steps such as expelling Russian diplomats.
Czech Prime Minister Andrej Babis said on March 23 that his country would "probably" expel Russian diplomats. Babis said he would consult with Foreign Minister Martin Stropnicky over the weekend and announce a decision on March 26.
Latvian Foreign Minister Edgars Rinkēvičs said his government "would support the United Kingdom" and could expel Russian spies operating under diplomatic cover, Latvian public broadcaster LSM reported.
"The concrete details will be coordinated [with other EU countries], and it could take place next week," Rinkēvičs said.
Meanwhile, a convoy of vehicles left the U.K. Embassy in Moscow on March 23, ahead of the Kremlin's deadline for 23 British diplomats to leave Russia, Reuters television footage showed.
Russia announced on March 17 that it was expelling 23 British diplomats in a retaliatory move against London, and gave the Britons a week to leave the country.
In addition to expelling the Russian diplomats, Britain has suspended high-level contacts with Moscow and said British ministers and royal family members will not attend the soccer World Cup in Russia in June and July.