Stoilov leaves Litex after European exit
Litex, Bulgarian champions in 1998 and 1999, were knocked out of the Europa League's playoff by Belarus champions BATE Borisov on Thursday.
"I have to do it because we've failed to achieve our goal," Stoilov told the club's website. "Also, the team didn't perform as I wanted."
Litex won the first leg in Belarus 1-0 but then suffered a humiliating 4-0 home loss after extra time in the return leg to leave the European competition with many local fans booing Stoilov and calling for his resignation.
Stoilov, 42, who was reappointed coach of Bulgaria in February, took charge of the Lovech-based club in June 2008, replacing Serbian Miodrag Jesic.