The Russian ambassadors to Poland and the Baltic states of Estonia, Latvia, and Lithuania have been summoned to meetings at those countries' foreign ministries, Russian news agencies report.
The reports on March 26, which cited various named and unnamed Russian diplomats, did not say whether reasons were given for the summonses.
They came amid signs that several European Union countries are preparing to expel Russian diplomats in response to the poisoning of a former Russian double agent Sergei Skripal and his daughter Yulia with a nerve toxin in England.
The two remain in critical condition after being found gravely ill on a bench in the southern English city of Salisbury on March 4.
Britain accuses Russian President Vladimir Putin's government of using a military-grade nerve agent that was developed during the Cold War -- part of a series known as Novichok -- to attack them with intent to kill.
On March 23, the EU collectively condemned the attack, said it was "highly likely" Moscow was responsible, and agreed to take further punitive measures.
Officials in the three Baltic states, Poland, and the Czech Republic said they are considering expelling Russian diplomats.
Czech Prime Minister Andrej Babis said on March 23 that his country would "probably" expel Russian diplomats and would announce a decision on March 26.
Meanwhile, several media outlets are reporting that U.S. President Donald Trump could be on the verge of expelling at least 20 Russian diplomats.
Citing unnamed sources, CNN and the Reuters news agency reported that a decision could come as soon as March 26 and would probably depend on moves by European countries.
Deputy White House Press Secretary Raj Shah told Bloomberg on March 24 that the "United States stands firmly with the United Kingdom in condemning Russia’s outrageous action."
"The president is always considering options to hold Russia accountable in response to its malign activities," Shah said. "We have no announcements at this time.”
Asked about the possibility of U.S. expulsions, Putin's spokesman said the Kremlin has seen no official announcements but suggested that Moscow would retaliate in kind if Washington kicks Russian diplomats out.
"Of course, in each such instance, the principle of reciprocity will be employed," spokesman Dmitry Peskov said.
Expulsions would display EU solidarity with Britain, which has expelled 23 Russian diplomats it said were spies in part of its response to the poisoning.
Speaking in Estonia on March 26, Britain's defense chief said that many Western countries are pushing back against Russian efforts to divide the West.
"What President Putin wishes to do is to divide Britain from its allies," Defense Secretary Gavin Williamson told reporters.
"The fact that right across the NATO alliance, right across the European Union, nations have stood up in support of the United Kingdom...I actually think that is the very best response that we could have," Williamson said.
Russia denies that it was behind the poisoning.
Moscow retaliated against the British expulsions by expelling 23 British diplomats, as well as taking other measures.
Skripal, 66, is a former Russian military intelligence officer who was convicted of treason in 2006 after a court found that he passed the identities of Russian intelligence agents to Britain's Secret Intelligence Service, MI6.
He was one of four Russian prisoners released in 2010 in exchange for 10 Russian sleeper agents uncovered in the United States in one of the biggest spy swaps since the Cold War.
He and his daughter fell ill one day after Yulia Skripal, 33, arrived on a visit from Moscow, where she had been living.
