BAGHDAD  Insurgents unleashed attacks across Baghdad on Tuesday night, setting off more than a dozen coordinated bombs in a bloody declaration of their ability to thwart the government’s efforts to secure Iraq’s largest and most important city.

It was among the fiercest assaults on the capital since the United States invaded in 2003, and one that tore across divisions of sect and class. The explosions  devastating car bombs and roadside blasts  struck the huge Shiite enclave of Sadr City, a Sunni mosque, public squares, a crowded restaurant in the north of Baghdad and middle-class shopping districts.

At least 63 people were killed and about 285 were wounded, and the local police said they were under orders to enforce an emergency curfew  the first such measure in years. But some police officers told residents that the curfew had not yet taken effect, while government officials would not confirm that one had been imposed.

“It was just storm and fire,” said Ahmed Said, 22, who said he was stirring his tea and ordering flavored tobacco at a cafe when he was hurled into the air.