Why Pussy Riot crashed the World Cup final - BBC News
Members of the group have already been held in custody for the stunt but could face further charges.
Members of the Russian protest-art group Pussy Riot have been instructed to report to police later this month, following their pitch invasion during the World Cup final.

They had already been detained for 15 days, but could now be facing fresh charges.

The group first shot to international prominence in 2012 when their punk protest against President Putin in a church ended in harsh prison sentences for three of its female members.