World football body, FIFA, has insisted there is no security threat to the forthcoming World football competition scheduled to hold in June this year in Russia.
This assurance follows the wake of violent incidents involving Spartak Moscow supporters on Thursday in which a policeman died of a heart attack.
The street battles had occured before their UEFA Europa League last 32 second leg tie at the San Mames stadium.
Nine people were arrested following the clashes.
Spanish newspaper El Mundo said two Russian ultras were taken to hospital with injuries, one with stab wounds.
The 2018 World Cup begins on June 14 in Russia and local authorities are putting strict security procedures in place to control hooligans, including Russian fans.