The strongest earthquake to hit Ecuador in decades flattened buildings and buckled highways along its Pacific coast.
President Rafael Correa said at least 233 people had died and rescuers were struggling to reach survivors trapped in the rubble.
The magnitude-7.8 quake, the strongest to hit Ecuador since 1979, was centered on Ecuador's sparsely populated fishing ports and tourist beaches, 105 miles (170 kilometers) northwest of Quito, the capital.
Correa reported the death toll on his official Twitter account while flying back from Rome to deal with the crisis. Officials earlier had reported more than 580 people injured.
Vice President Jorge Glas said there were deaths in the cities of Manta, Portoviejo and Guayaquil all several hundred kilometers (miles) from the center of the quake struck shortly after nightfall yesterday.
In Pedernales, a town of 40,000 near the quake's epicenter, dozens of scared residents slept in the streets while men equipped with little more than car headlights tried to rescue survivors who could be heard trapped under rubble.
"We're trying to do the most we can, but there's almost nothing we can do," said Gabriel Alcivar, mayor of Pedernales.
Alcivar pleaded for authorities to send earth-moving machines and emergency rescue workers to help find people amid the rubble. He said looting had broken out amid the chaos but authorities were too busy trying to save lives to re-establish order.
"This wasn't just a house that collapsed, it was an entire town," he said.
Correa declared a national emergency and urged Ecuadoreans to stay strong while authorities handle the disaster.
"Everything can be rebuilt, but what can't be rebuilt are human lives, and that's the most painful," he said in a telephone call to state TV before departing Rome straight for Manta.
Glas said 10,000 armed forces had been deployed to help. In addition, 4,600 national police were sent to the towns near the epicenter.
Officials said shelters had been set up and field hospitals were being deployed in Pedernales and Portoviejo.
More than 3,000 packages of food and nearly 8,000 sleeping kits were being delivered. Electricity in Manabi province, the hardest hit, remained mostly down as authorities focused on finding survivors.
"Compatriots: Unity, strength and prayer," Glas told a throng of residents gathered in the streets of Manta as he instructed them on how to look for survivors. "We need to be quiet so we can hear. We can't use heavy machinery because it can be very tragic for those who are injured."
Homes were reduced to rubble along the quake's path, while in Guayaquil a shopping center's roof fell down and a collapsed highway overpass crushed a car.
