SOFIA, Bulgaria -- England's 6-0 Euro 2020 qualifying win against Bulgaria was temporarily halted during the first half of the Group A fixture in order to warn supporters that the match could be abandoned following racist chanting in the Vasil Levski Stadium.

Match referee Ivan Bebek instructed the stadium PA announcer to broadcast the message -- the first step in FIFA's three-step protocol when dealing with such incidents -- after England defender Tyrone Mings complained of being the subject of racist chanting in the 22nd minute.

Bulgaria supporters in the crowd were seen directing monkey chants at England players, doing Nazi salutes and holding up shirts with the UEFA logo and the text "No Respect" -- a reference to the European governing body's "Respect" campaign aimed at curbing racism in the sport.

England manager Gareth Southgate then alerted the fourth official, Mario Zebec, who passed the information on to the referee.

The message, delivered in both Bulgarian and English, called for a stop to "racist behaviour" with the warning that the game could be abandoned if there were further outbreaks.

The match then continued, but play was stopped again on 41 minutes, when Southgate was involved in another lengthy discussion with the referee.

Following the match, Southgate told the BBC: "It's been an incredible few days really. We had to prepare for this eventuality. The most important thing was the players and staff knew what we were going to do and were in agreement.

"Nobody should have to experience what our players did. We followed the protocol. We gave two messages -- one that our football did the talking and two, we stopped the game twice.

"I have to give credit because the referee communicated with us all the time. You heard the stadium announcement on the first instance. In the second instance, we could have walked off but the players were very keen to finish the first half and talk it through.

"Not one player wanted to stop, they were absolutely firm on that."

Bulgaria manager Krasimir Balakov insisted he didn't hear the abuse, but added: "If it's proven to be true, we have to be ashamed of it and apologise."

Bulgarian captain Ivelin Popov was seen talking to fans through the metal fence at the break and a number of people were seen leaving the stands.

The game was already being played in front of a reduced crowd after UEFA ordered a partial closure due to racist behaviour by their supporters in June's qualifiers against the Czechs and Kosovo.

England forward Marcus Rashford took to Twitter following the match to thank England supporters and to praise the actions of Popov, crediting him for the courage it took to stand up in the face of the abuse.

Also been told what the Bulgaria captain did at half-time. To stand alone and do the right thing takes courage and acts like that shouldn't go unnoticed. #NoToRacism

— Marcus Rashford (@MarcusRashford) October 14, 2019

Following the match, England FA chairman Greg Clarke told ITV: "I was up in the stands with some of the FA staff and we were watching the game and heard a sound which sounded like monkey chanting, we can't be sure.

"I came down and heard some more at the side of the pitch and saw some activity by a group of people dressed in black by a corner flag and it was appalling. I checked the team was OK and that Gareth was OK and the second half went ahead on that basis.

"We were told by officials that 50 people -- the people in the corner -- were thrown out at half-time. I asked why the other issues were not dealt with and they said they were isolated incidents not mass incidents and the protocol deals with mass incidents."

The FA also released the following statement after the match: "The FA can confirm that England players were subjected to abhorrent racist chanting while playing in the EURO 2020 qualifier against Bulgaria. This is unacceptable at any level of the game and our immediate focus is supporting the players and staff involved.

"As we are sadly aware, this is not the first time our players have been subjected to this level of abuse and there is no place for this kind of behaviour in society, let alone in football. We will be asking UEFA to investigate as a matter of urgency."

England player Tammy Abraham said last week that he and his teammates would walk off the pitch if racist chanting happened while playing for their country.

However, Raheem Sterling and Southgate subsequently insisted that the squad would "place faith in UEFA" by leaving the match officials to take the lead if any incident occurred.

Before the match Bulgaria's football chief Borislav Mihaylov said England players should face consequences if they breach UEFA protocols in the qualifying matches and expressed his "extreme disappointment" at the England players' comments ahead of the match and spoke of the "unjust branding" of local fans.

Anti-racism and discrimination group Kick It Out also issued a statement following the match to express their extreme disappointment with the behaviour on display during the match.

The statement read in part: "We are sickened by the disgusting racist abuse directed at England men's team tonight by Bulgaria supporters - including TV footage which appeared to show Nazi salutes and monkey noises.

"We applaud Gareth Southgate, his staff and players for the actions taken in reporting the abhorrent abuse, and offer our full support to the entire squad, their families and anyone affected by those appalling scenes."

Step one of the three-step protocol involves a message played over the PA system, with step two seeing the referee take the teams off the pitch for a period of time.

If the players return to action and another incident of racist behaviour occurs, the game is then abandoned as the third step of the protocol.

Information from Reuters and the Associated Press was used in this story.