Protesters from a group known as the Syria Campaign blocked the entrance to Russia's embassy in London on November 3 with 800 mannequin limbs, a move they said was taken in response to the killing of hundreds of civilians in the Syrian city of Aleppo.
Two people also chained themselves to the gates.
The Russian Embassy protested that it was "deeply concerned" about the unwillingness of the U.K. government to "ensure security and unhindered operation of the Russian diplomatic mission in London."
It said staff and visitors were unable to enter the embassy because of the protesters, and London police were "indifferent" despite the demonstrators' "provocative and disorderly conduct."
The embassy also said its telephone lines were clogged by "nuisance callers."
The embassy accused the government of waging an anti-Russian campaign by encouraging people to protest outside the embassy.
Bissan Fakih from the Syria Campaign said campaigners wanted to highlight that Russian warplanes "are killing so many families" and that the bombing "needs to stop."
"The people of the world are watching," she said.