Nine arrests made after Bilbao v Spartak fan violence

Spanish Prime Minister Mariano Rajoy offered his condolences for the death of the 51-year-old Basque police officer and "strongly condemned" the violence in the northern Spanish city on Thursday.

The officer was one of over 500 police officers deployed to the San Mames stadium in Bilbao for the high-risk return leg of the tie.

He "suddenly felt ill during the serious incidents... despite being taken quickly to hospital, he suffered cardiac arrest," the Basque government's security department said in a statement, adding his death was not "directly" linked to an injury he suffered in the clashes.

The trouble began as Spartak 'ultras' arrived at the stadium.

Some lit and threw smoke bombs and garbage cans towards Athletic supporters, before police charged them.

Police detained five Spaniards, three Russians and a Polish man over the clashes, a spokesman for the Basque security department said. They face charges of causing a public disorder, rioting and disrespect for authority.

Five police officers were injured, none of them seriously, and treated on the scene, the spokeswoman added.

There was concern ahead of the match because of the reported presence of hardcore Russian fans in Bilbao, and police seized knives, bags full of rocks and brass knuckles from supporters of the two teams, the Basque security department said.

Earlier Thursday, German police arrested a Russian suspected of the "attempted murder" of a British football fan during the European Championship in France two years ago. He was detained at Munich airport as he was trying to travel to Bilbao to attend the match, according to German police.

But a spokesman for Russia's embassy in Germany, Denis Mikerine, "strongly protested" the arrest on Facebook, saying it was a "possible pretext" to "politicise the theme of football hooliganism before the 2018 World Cup in Russia".

Russian authorities will be on high alert this summer for the World Cup after Russian fans were involved in pitched battles with England supporters in Marseille during Euro 2016.

FIFA said Friday it "deeply regrets" the clashes in Bilbao but had "complete trust" in Russia's ability to ensure a safe World Cup.

Spartak won Thursday's match 2-1, but Bilbao went through 4-3 on aggregate.