"We'll give two balls, which were used in the encounters between Croatia and Nigeria, and Serbia and Switzerland, to our youth athletic center and to our sports museum... so that they remind young citizens of Kaliningrad of the wonderful event that took place in our city," Head of Kaliningrad Region's Administration Aleksey Silanov said, as quoted by the press service.

Each ball features inscriptions with the date of the match and the participating teams.

The 2018 FIFA World Cup kicked off on June 14 and will continue until July 15, with the matches being played in 11 cities across Russia. The knockout stage of the tournament will start on Saturday.