Three cheers for the FBI.

“Russians forward! F**k the Caucasus,” Lokomotiv fans began to chant at a qualifying match on 23 August 2012 between the Dutch club AZ Alkmaar and Anzhi Makhachkala, a team from Russia’s mostly Muslim Caucasus region that were renting the Lokomotiv stadium in Moscow.

Police detained some 80 fans and Anzhi went on to win the game. But after their victory groups of hooligans attacked Anzhi fans in the metro station Chistye Prudy, splattering the platform in blood. A Russian nationalist organisation later said on social media that 70 Lokomotiv fans had taken part in the assault using traumatic pistols (handguns that fire rubber bullets).

As Russia gears up to host the 2018 World Cup, concerns have been raised about the spiralling costs for the tournament and alleged corruption during the Fifa bidding process. Last week Alexander Khinshtein, of the ruling United Russia Party, announced legislative amendments that would allow inmates to perform forced labour outside their prison colonies, a move he said could help save money on World Cup construction.

But racist incidents like those at the Anzhi-AZ match, which came a day after a group of 50 young people attacked Anzhi fans in St Petersburg on their way to watch a game, have added worries about the reception non-white players and even supporters could receive in Russia.

A recent report by the Fare network and the Moscow-based Sova Centre for information and analysis has documented 99 racist and far-right displays and 21 racially motivated attacks by Russian football fans during the 2012-13 and 2013-14 seasons.

A new leaked letter appears to show South African authorities seeking an indirect route for the transfer of $10m (£6.5m) to Fifa.

The letter carried by South African media was purportedly written by then SA FA president Danny Jordaan three weeks before the first amount was paid.

US prosecutors say the money was a bribe to Fifa officials to help secure South Africa's 2010 World Cup bid.

South Africa says it was a legitimate payment to fund Caribbean football.

The $10m payment is a key plank in the wide-ranging US criminal inquiry that has engulfed world football's governing body.

Seven top Fifa officials, including two vice-presidents were arrested last week in Switzerland as they awaited Fifa's congress.

They were among 14 new indictments in the US investigation, which alleges they accepted bribes and kickbacks estimated at more than $150m over a 24-year period.

Four other people were charged earlier. One of them, ex-Fifa official Chuck Blazer, has pleaded guilty in the US to taking bribes related to South Africa's bid.

Russia and Qatar could lose the 2018 and 2022 World Cups respectively if evidence emerges of bribery, leading Fifa official Domenico Scala has said.

The countries deny wrongdoing in their bidding processes and Scala admits he has not seen evidence of corruption.

Scala is the head of Fifa's audit and compliance committee.

But he said: "Should there be evidence that the awards to Qatar and Russia came only because of bought votes, then the awards could be cancelled."

Speaking to Swiss newspaper Sonntagszeitung, he added: "Until today, the respective evidence has not been provided."

Scala made similar comments at the end of 2013 but in light of events at Fifa in the past two weeks this will be viewed as a more serious warning.