MOSCOW, February 20. /TASS/. The US embassy in Moscow has warned American nationals about alleged threats of terror attacks in public places in Moscow and St. Petersburg, as well as in areas near the Russian-Ukrainian border.

"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 embassy said in a press statement on its official website on Sunday.

However, it cited no concrete media source to back its warning.

The embassy recommended US nationals follow publications in international mass media, avoid places of public gathering, inform their friends and families about their security, avoid contacts with unknown persons, and "stay alert in locations frequented by tourists/Westerners."

It also advised to "have evacuation plans that do not rely on U.S. government assistance.".