A huge Latin letter 'Z' and 'V' -- symbols used by the Russian military which have been adopted by high-profile supporters of Russia's offensive -- were put up outside the entrance of the embassy on one of Moscow's main ring roads.

Russia has severed ties with the West amid its military campaign in Ukraine, which has dragged on for more than 21 months.

The letters are the latest pro-Kremlin symbols to be put on the US embassy's doorstep, where nationalist activists have for years placed imagery backing Moscow's anti-Western foreign policy.

Several Western countries have renamed streets where the local Russian embassy sits in support of Ukraine or Kremlin critics in recent years.

In Washington, the street where the Russian embassy is located was renamed in honour of slain Russian politician Boris Nemtsov.

Ties between Moscow and Washington have sunk to their lowest since the Cold War, with the US and its allies levelling an unprecedented package of sanctions on Moscow since it launched its campaign.

The US is also arming Ukraine to help it battle the Russian offensive.