WASHINGTON — The Pentagon released an aerial photo on Friday of a pulverized building in Syria in an unusual defense of an American airstrike that officials said killed dozens of Al Qaeda operatives at a meeting place — and not civilians at a mosque, as activists and local residents maintain.

Far from settling the debate, however, the photo prompted fresh challenges from local activists who argued that the building was part of a religious complex. Some of them distributed their own photos of the devastation, fueling the dueling narratives.

The Pentagon has not said which Qaeda leaders it believes were killed in the strike but suggested it might make that information public once it receives confirmation. The Syrian Observatory for Human Rights said that 49 people had been killed in what the group described as a “massacre” of civilians who were undergoing religious instruction.

Capt. Jeff Davis, a Pentagon spokesman, said officials had watched the building “for some time” before unleashing a barrage of missiles and bombs after evening prayers on Thursday. He said dozens of militants had been killed in the strike on the building in the Syrian village of Al Jinah, in Aleppo Province.