A Euro 2020 qualifier between England and Bulgaria was temporarily halted on two occasions on Thursday evening after racist chants were heard from the stands.
Bulgaria's football union chief has resigned after racist abuse marred an Euro 2020 qualifier match in Sofia.
A statement on the union's website on behalf of Borislav Mihaylov cited "recent tensions" and "an environment that is detrimental to Bulgarian football and the Bulgarian Football Union".
It added: "After many years spent in the post and with his many contacts at a high international level, Mr Milaylov expresses his firm readiness to continue helping in the development of Bulgarian football in every possible way."
The resignation comes a day after racist abuse from the stands forced an international match against England to be halted twice.
Monkey chants were heard from the crowd on Monday evening as England's back players were in possession of the ball, while footage showed hooded men in the home end shouting and performing Nazi saltues.
After the referee's second halt to the game, the men were seen being escorted to the exit — and England went on to win the game 6-0.
Widespread anger toward the racist behaviour dominated the conversation during and after the match, and among them was Bulgarian Prime Minister Boyko Borissov, who demanded Mihaylov's resignation.
“I urge Borislav Mihaylov to immediately resign as president of the Bulgarian Football Union!” Borissov posted on Facebook.
“It is unacceptable for Bulgaria, which is one of the most tolerant countries in the world, and people of different ethnicities and religions live in peace, to be associated with racism and xenophobia.”
Earlier Sports Minister Krasen Kralev said the government would suspend relations with the BFU, including financial ties.
The Bulgarian Football Union (BFU) was not immediately available to comment after the match. However, it tried to play down the incidents.
“It’s quite disappointing to focus on racism,” BFU vice-president Yordan Lechkov said. “It’s not serious to concentrate on that if there’s a qualifier like this and we’re playing against a team like England.”
A spokesman for UK Prime Minister Boris Johnson said the racism in Sofia was vile.
In response to reports that Bulgarian captain Ivelin Popov had begged Bulgarian fans at half time to stop the abuse, sports broadcaster Gary Lineker said: "Good for him. It needs to come from the home players.
"Imagine thinking you're in any way superior due to the colour of your skin. Such ignorance."
Peterborough United coach Aaron Mclean said the behaviour was "disgusting and shameful" but said he also wasn't surprised.
"It's not gonna change anytime soon," he said, before praising England's players for their handling of the situation.
Other sports commentators looked toward UEFA's overall strategy of tackling racism on the pitch, suggesting that anti-racism banners and hashtags were too light of an approach.
"This [behaviour] is partly the result of UEFA being so supine for so long towards racist behaviour," The Times Sport chief footballer writer Henry Winter wrote on Twitter.
He added: "You can't fight bigots with "respect" banners, hashtags, terrace closures and fines.
"Games should be stopped, and the hosts and their fans shamed. Players should walk off."
UEFA also has a three-step set of protocols for dealing with racism, which was used in the game on Thursday evening.
The first step sees the referee temporarily halt the game to ask for an announcement demanding the racist behaviour to stop.
A second time would see the game halted for a longer period and another announcement to the stadium.
In the case of repeated racist behaviour after this, the match should be called off entirely.
But former professional footballer Marvin Sordell said future generations would wonder why the idea of players leaving the pitch after repeated abuse would ever be subject to discussion.
"It's absolute madness to just continue to do your job and basically accept being racially abused whilst doing it," he said.