The U.S. ambassador to Russia, John Sullivan, arrived at Russia's foreign ministry on Wednesday along with Polish ambassador Krzysztof Krajewski, RIA news agency reported.

Krajewski had been summoned to the foreign ministry after protesters poured red liquid over Russia's envoy to Poland at a wreath-laying ceremony in Warsaw on Monday, Poland's PAP news agency reported.

(Reporting by Reuters; Editing by Kevin Liffey)