A surgeon, who asked not to be identified for fear of reprisals, said that for hours on Thursday the Health Ministry prevented ambulances even from going to the scene to aid victims. The doctor said that in the early morning, when the assault was still under way, police officers beat a paramedic and a doctor and refused to allow medical staff to attend to the wounded. News agencies in Bahrain reported that the health minister, Faisal al-Hamar, resigned after doctors staged a demonstration to protest his order barring ambulances from going to the square.

In the bloodstained morgue, Ahmed Abutaki, 29, held his younger brother’s cold hand, tearfully recalling the last time they spoke Wednesday night. “He said, ‘This is my chance, to have a say, so that maybe our country will do something for us,’ ” he recalled of his brother’s decision to camp out in the circle. “My country did do something; it killed him.”

There was collective anxiety as Friday approached and people waited to see whether the opposition would challenge the government’s edict to stay off the streets  and if it did, whether the government would follow through on its threat to use “every strict measure and deterrent necessary to preserve security and general order.” Both sides said they would not back down.

“You will find members of Al Wefaq willing to be killed, as our people have been killed,” said Khalil Ebrahim al-Marzooq, one of 18 opposition party members to announce Thursday that they had resigned their seats. “We will stand behind the people until the complete fulfillment of our demands.”

Arab leaders have been badly shaken in recent days, with entrenched leaders in Egypt and Tunisia ousted by popular uprisings and with demonstrations flaring around the region. And now as the public’s sense of empowerment has spread, the call to change has reached into this kingdom. That has raised anxiety in Saudi Arabia, which is connected to Bahrain by a bridge, and Kuwait, as well, and officials from the Gulf Cooperation Council met here to discuss how to handle the crisis.