A senior British police officer has revealed there were fears that five England fans would die after being attacked by Russian hooligans during "barbaric" scenes in Marseille at Euro 2016.
England's opening match of the tournament against Russia on June 11 was marred by violent clashes between supporters -- inside and outside the Stade Velodrome -- raising concerns ahead of the 2018 World Cup, which is to be staged in Russia.
Chief superintendent Steve Neill of Northumbria Police, the senior British police officer in Marseille, has described the scenes as "football hooliganism on a different level" and that police were forced to "activate the counter-terrorism plan."
"The Russians came with serious intent to carry out barbaric violence," Neill said in an interview with Sky News. "They were highly organised, very effective and we saw football hooliganism on a different level.
"I couldn't believe what I was seeing. It was like a herd of wildebeest rampaging through tables and chairs, fights going off, people being kicked on the ground by groups of five or six men.
"The severity and barbarity of it was quite shocking. There was CS smoke drifting everywhere, tables and chairs lying around, people with blood pouring out of their heads. It was like nothing we had seen before."
England and Russia fans clashed in the Old Port area of Marseille, which had also witnessed violence during the 1998 World Cup when England played Tunisia at the Stade Velodrome.
Following the trouble, some 30 England supporters were hospitalised, with several having sustained life-changing injuries.
Ultimately there were no fatalities, but Neill admitted British police were left fearing the opposite at the time.
"On the Saturday we had over 100 walking wounded, 30 seriously who had been admitted to hospital, and five who the consultant told my officers were likely to prove fatal that evening," he said.
"I stood in Marseille as the senior officer believing we were going to get five fatalities that night, we might have five murders on our hands. It was unprecedented, so we activated the counter-terrorism plan."
British police have already begun planning for the World Cup in Russia. They met with Foreign Office officials earlier this month and are set to inform supporters over whether or not it will be safe to travel.
Assistant chief constable Mark Roberts said in an interview with Sky News that he has confidence the Russian authorities will be able to deal with any such instances of disorder on their own soil.
Roberts, the national lead for football policing, also said that banning orders against England fans identified as having engaged in disorder would be sought ahead of the 2018 World Cup.
Assurances will also be required that travel to Russia will be safe for supporters of the Home Nations, all of whom are currently in the initial stages of attempting to qualify for the tournament.
"What we saw in Marseille is that there are groups of Russian supporters who are where we were in the 1980s, or perhaps beyond that, so there is that threat," Roberts said. "But I have got confidence in the Russian police to deal with this. They manage it in their domestic football, though there are some instances.
"We will not give advice to the fans that I am not happy to stand behind, so if we identify risks we will tell the supporters so they can make informed decisions. If we have a high degree of confidence that they can travel without issue, that will be the message."