The shooting took place at a Greek Orthodox church in Karak, about 110 miles south of the capital, Amman.
Footage broadcast on Jordanian state television showed two gunmen who appear to be holding pistols approaching the church and firing shots. A third man who appears to be holding a semiautomatic rifle then approaches and opens fire, and all three then run toward the church.
Video footage taken by witnesses shows broken glass and pools of blood on the floor of the church.
Dorgham Halasa, who was among the mourners inside the church, said intense gunfire erupted 15 minutes after the funeral had started, and then people started running. “It was a weird situation, and heavy gunfire,” Halasa said.
He did not see the gunmen, but said other people reported seeing four of them. The Associated Press could not independently verify the number of assailants, and Jordan’s security services did not immediately release details.
A government statement said that the attack was “carried out by unknown assailants,” but didn't say whether any gunmen were captured or killed. It said that “investigations are underway at full speed.”
Jordan declared three days of national mourning, according to the kingdom’s Petra News Agency.
Karak is home to a minority Christian population.
