The United States warned nationals in Russia to have evacuation plans, citing the threat of attacks in Moscow amid ongoing tensions with Ukraine.
"There have been threats of attacks against shopping centers, railway and metro stations, and other public gathering places in major urban areas, including Moscow and St. Petersburg as well as in areas of heightened tension along the Russian border with Ukraine," the embassy said.
"Review your personal security plans," the embassy said. "Have evacuation plans that do not rely on U.S. government assistance."
Russia's foreign ministry spokesperson, Maria Zakharova, questioned if the United States had passed on the information about possible attacks to Russia.
"And if not, how is one to understand all of this?" Zakharova said.
On Sunday, U.S. Secretary of State Antony Blinken warned that Russia was on the brink of invading Ukraine.
Russia extended military drills near Ukraine's northern borders Sunday amid increased fears that two days of sustained shelling along the contact line between soldiers and Russia-backed separatists in eastern Ukraine could spark an invasion. Ukraine's president appealed for a cease-fire.
The exercises were originally set to end Sunday and brought a sizable contingent of Russian forces to Belarus. The presence of the Russian troops raised concern that they could be used to sweep down on the Ukrainian capital, Kyiv, a city of about 3 million people less than a three-hour drive away.
Western leaders warned that Russia was poised to attack its neighbor, which is surrounded on three sides by about 150,000 Russian soldiers, warplanes and equipment. Russia held nuclear drills Saturday as well as the conventional exercises in Belarus, and has ongoing naval drills off the coast in the Black Sea.