Bulgaria's football chief resigned on Tuesday after racist chanting marred England's Euro 2020 qualifier in Sofia, as UEFA chief Aleksander Ceferin said the sport needed to "wage war" on abusers.

England eased to a 6-0 victory over their hosts in the Bulgarian capital on Monday but the game was blighted by offensive chants, forcing the match to be halted twice in the first half.

British Prime Minister Boris Johnson condemned the "vile" racism, which included monkey noises and apparent Nazi salutes, and called for tough action from UEFA.

As temperatures rose his Bulgarian counterpart, Boyko Borisov, urged the country's football union president to quit.

"I urge Borislav Mihaylov to hand in his resignation immediately!" Borisov wrote on Facebook, adding it was "inadmissible that Bulgaria... is associated with racism and xenophobia".

Hours later the Bulgarian Football Union said in a statement Mihaylov had offered his resignation and would hand it to the members of the BFU executive committee on Friday, citing "tension created over the past days, which is detrimental to Bulgarian football".

His resignation came shortly before the BFU's headquarters were raided by special prosecutors and police, although it is not clear if the swoop was related to Mihaylov's resignation or Monday night's abuse of England's black players.

Shortly before UEFA announced it had launched a probe into the behaviour of the Bulgarian fans, its president Ceferin stressed the commitment of European football's governing body to root out the "disease" of racism.

"More broadly, the football family -- everyone from administrators to players, coaches and fans -- needs to work with governments and NGOs to wage war on the racists and to marginalise their abhorrent views to the fringes of society," he said.

Earlier, a spokesman for prime minister Johnson said: "The racism we saw and heard last night was vile and has no place in football or anywhere else.

"The England players and management showed tremendous dignity and the prime minister commends the players who were targeted with this despicable abuse for their response."

After several English players suffered racist abuse in a qualifier away to Montenegro in March, England manager Gareth Southgate had prepared his side to follow UEFA's three-step protocol for reporting racist incidents that can lead to matches being abandoned.

England captain Harry Kane said the team had made a decision to carry on playing but called for tougher punishments.

"Whether the UEFA protocol is strong enough, I'm not sure," he said.

"Whether any racial abuse should be allowed at any time... well it shouldn't be. The protocol at the moment allows there to be an announcement, there to be two or three steps before the players are taken off the pitch.

"It's unacceptable to be racist once so I feel there can be stronger punishment, stronger protocols but from our point of view as a team we stuck together, we showed unity and we did what we wanted to do."

British anti-racism group Kick It Out said the game should have been abandoned by officials after TV footage showed that racist abuse continued in the second half.

"There can be no more pitiful fines or short stadium bans," the group said. "If UEFA care at all about tackling discrimination... then points deductions and tournament expulsion must follow."

A section of 5,000 seats at the Vasil Levski National Stadium was already closed for the game after racist incidents during games against Kosovo and the Czech Republic in June.

With England 2-0 ahead, the game was temporarily stopped and a warning played over the loudspeakers in both Bulgarian and English.

That warning was not heeded and there was a second, longer stoppage of the match after Ross Barkley put England 3-0 up, with a number of Bulgarian 'ultra' fans ejected from the stadium.

England now need just a point from their final two qualifiers against Montenegro and Kosovo next month to seal their place at next year's Euros.

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