A Romanian baby died after a baptismal ceremony in which babies were immersed in holy water three times.
The six-week-old baby was rushed to a hospital on Monday with a cardiac arrest and died a few hours later.
The tragedy put pressure on the Orthodox Church to change the rules of baptism.
Prosecutors have opened an inquest against the priest in the city of Suceava.
“The death of a newborn baby as a result of this practice is a great tragedy,” reads a message with an online petition for changes to the ritual. “This risk must be ruled out in order for the joy of baptism to prevail.”
According to AFP, the petition had collected more than 56,000 signatures by Thursday evening.
One person online exposed the ‘brutality’ of the ritual and another exploded the ‘stubbornness of those who think it is God’s will’ to uphold it.
Local media have reported on several similar incidents in recent years.
Church spokeswoman Vasile Banescu said priests could pour some water on a baby’s forehead instead of the full immersion.
But Archbishop Theodosia, leader of the church’s traditionalist wing, stood firm and insisted that the full ritual would not change.
In Romania, where more than 80 percent of the population is Orthodox, the church is one of the most trusted institutions, according to recent opinion polls.