The apparent satirical protest came after the Russian-language version of the plaque was removed this week following complaints about its inscription: "In eternal memory and honor of the fallen soldiers, internationalists, and peacemakers."
The word "internationalists" was taken by Czechs to include the Soviet troops who occupied Czechoslovakia from 1968 until 1991, when the last Soviet soldiers left the country.
The memorial in Olsany Cemetery was built by a St. Petersburg-based group for Russian veterans of the Soviet war in Afghanistan.
On March 21, an unidentified man was photographed placing toy tanks and red soldiers on the memorial and on the ground in front of it. One toy soldier was holding a Soviet flag.
In addition, "CZ" has been spray-painted on the blank spot left on the plinth after the plaque's removal.
A Czech version of the plaque honoring "fallen soldiers and peacemakers" is still in place.
-- Antoine Blua, with contributions by RFE/RL's Belarus Service correspondent Alena Kovarova