Krasimir Balakov has quit as Bulgaria coach in the wake of the 6-0 Euro 2020 qualifying defeat to England which was marred by racist abuse.
England's black players were targeted by monkey chanting in Monday night's match, which Balakov said he had not heard.
He later issued a statement apologising to the England players and to anyone offended by the abusive chanting.
A spokesman for the Bulgarian Football Union confirmed to the PA news agency on Friday afternoon that Balakov, who featured for his country in their run to the World Cup semi-finals in 1994, had tendered his resignation.
"The performance of Bulgaria's men's national team in recent months has been described as unsatisfactory, which is why the national coach Krasimir Balakov resigned," the BFU said in a statement.
"I am no longer a national team coach and I wish success to the next coach. At the moment, the situation is not rosy," Balakov said, in quotes reported by sportal.bg.
"I'm a professional and I know there are times like this in my life. I will look for my next chance. I will rest now."
Borislav Mihaylov resigned as president of the BFU on Tuesday, and later that day the association was charged over the racist behaviour of its fans against England by UEFA, a case which will be heard on October 28.
The BFU announced on Friday that Mihail Kasabov had taken the presidency on a temporary basis, after vice-presidents Yordan Lechkov and Atanas Furnadzhiev had declined to take it on.
Kasabov will now need to organise an extraordinary congress to elect a new executive committee, the BFU statement said.
Five more men were arrested on Friday over the events of Monday night.
They were detained at the First District police station in Sofia while a further five were searched at a different precinct in the Bulgarian capital, taking the total number identified to 16, a spokeswoman for the ministry of the interior told the PA news agency.
Six supporters were arrested on Wednesday, with four already having been banned from attending any sporting event for the next two years and fined 1,000 lev (around £440). One individual was due to attend a pre-trial hearing on Friday and could be remanded in custody.
The ministry spokeswoman said the search to identify further individuals continues.
The referee initiated the first step of UEFA's anti-racism protocol just before the half-hour mark by asking for a public address announcement in the stadium ordering the racist behaviour to stop.
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