Five people died and two were severely injured in the self-immolations in protest against poverty and corruption, the BBC reported Friday.
In his appeal, President Rosen Plevneliev urged people to pray for "an end to the suicides and for passing through the crisis with patience and dignity."
The president added, "Faith has preserved our nation over the centuries. And it will now help us to believe in our strength and our future."
Special prayers will be held across the country Friday, Saturday and Sunday. They will be led by leaders of the Christian Orthodox, Catholic, Armenian, Protestant, Muslim and Jewish faiths.
Almost 200 people have committed suicide this year in Bulgaria, Europe's poorest country, said Dr. Vladimir Nakov of the National Health Centre.
The previous government was forced to resign in February after weeks of protest over high electricity bills, poverty and corruption.