“They are shooting,” a person at the mosque said by telephone, referring to the soldiers and other security forces. “Killing and killing and more killing.”

A doctor at the city’s main hospital, Ali Nassab al-Mahameed, was shot and killed as he was trying to rescue others, the witness said. It was not known how many people were wounded in the attack.

“It seems that security forces may be trying to storm the complex,” a resident told Reuters. “It is not clear because electricity has been cut off. Tear gas is also being used.”

The mosque’s preacher, Ahmad Siasneh, told Al Arabiya television on Tuesday that Syrian forces were close to the building’s grounds, where protesters had erected tents.