The US Embassy in Moscow has urged its citizens to refrain from travels to Russia amid possible terrorist attacks in Moscow and Saint Petersburg over the escalation of the Ukrainian crisis.
"According to media sources, 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 diplomatic mission said in a statement published on its official website on Sunday.
The embassy did not specify what sources it used to issue a notice, and made some recommendations, including to monitor local and international media for updates, avoid crowds, keep in touch with friends and family, and mind the surroundings.
It also advised to stay alert in locations frequented by tourists and Westerners, review personal security plans, carry proper identification, including a US passport with a current Russian visa, and have evacuation plans that do not rely on US government assistance.
Commenting on the warning, Russian Foreign Ministry spokeswoman Maria Zakharova asked whether the US diplomats shared with the relevant Russian law enforcement the information about planned terrorist attacks.
"If not, how to understand all this?" she questioned on Sunday.
Meanwhile, Kremlin spokesman Dmitry Peskov said the US embassy information about possible terrorist attacks is being investigated.
"This is a very, very unusual practice, such publications by diplomatic missions. We are looking into whether there were any signals from the Americans (about possible terrorist attacks) through the special services. I am currently unaware that such signals took place," he told reporters at a daily briefing in Moscow on Monday.
US President Joe Biden said on Friday that Russia is on the brink of invading Ukraine within "several days".
Tensions have risen dramatically in eastern Ukraine over the past days, with a growing number of cease-fire violations, multiple shelling incidents, and evacuation of civilians from the pro-Russian separatist regions of Donetsk and Luhansk.
Western countries have accused Russia of amassing more than 100,000 troops near Ukraine, prompting fears that it could be planning a military offensive against its ex-Soviet neighbor.
Moscow has repeatedly denied any plan to invade Ukraine and instead accused Western countries of undermining Russia's security through NATO's expansion toward its borders.
It also issued a list of security demands to the West, including a rollback of troop deployments from some ex-Soviet states and guarantees of NATO's further non-expansion.