Levski, who will mark their 100th anniversary next year, were knocked out of the competition by unfancied Kazakhstan side Irtysh Pavlodar 2-0 on aggregate.
Irtysh are sixth in the Kazakhstan's league after 18 matches and they equalled their best European achievement by reaching the Europa League's second qualifying round.
"One thing is certain - Mitov will not be coach of Levski," club's chief executive Nasko Sirakov told Darik radio as the team has yet to return to Bulgaria. "I had a discussion with him and we reached a decision.
"We must look for another solution," added Sirakov. "I wish him success but Levski will have a new coach.
"We'll release some players, that's for sure while another will be sold. There are players who don't deserve to be in the team."
In April, former Levski winger and academy coach Mitov replaced Ilian Iliev, who left the club following a string of poor results.
The Blues, as Levski are known in the Balkan country, were lambasted by local media after the humiliating exit while fans called it "the most shameful failure in the club's history".
- Sports & Recreation
- Nasko Sirakov