TOCOPILLA, Chile — Strong aftershocks from a powerful earthquake hit northern Chile today as the government erected a working military hospital and promised hundreds of other portable dwellings for 15,000 left homeless by the quake.

Government and army workers scrambled to distribute tons of food, water and medicine after the 7.7 magnitude quake struck near the desert village of Quillagua in the foothills of the Andes yesterday, killing at least two people and injuring more than 150.

Major aftershocks shook the region today, including one of magnitude 6.2 and another of magnitude 6.8, the U.S. Geological Survey said. There were no immediate reports of further damage or injuries.

The earthquake destroyed or damaged 4,000 houses and the local hospital, blocking roads, crushing cars and knocking out power across northern Chile, officials said.

This port city of 27,000 and the nearby mining town of Maria Elena were the hardest hit, and a presidential spokesman, Ricardo Lagos Weber, said both would be declared disaster areas to expedite aid delivery.

Four Cabinet ministers were in the area coordinating recovery and aid efforts. President Bachelet also flew there today, meeting with residents in a debris-strewn Tocopilla street when the strongest aftershock hit. Her bodyguards watched warily as power posts swung around her, but the president remained calm.

Residents shouted and held up signs demanding help, and Ms. Bachelet assured them that the government would issue both credits and grants. She said it would take a month to assess the damage.

“There is much fear and despair, and that is normal,” Ms. Bachelet told them. “But people should organize and respond to emergency plans.”

The president was accompanied by four cabinet chiefs including Housing Minister Patricia Poblete, who said many structures cannot be saved. Firefighters and other workers began demolishing the most severely damaged homes.

Dr. Cristian Castillo said “80% of our hospital is useless.”

Two women were killed in Tocopilla, 25 miles from the epicenter, when their houses collapsed, authorities said. Hospital director Juan Urrutia said at least 117 people were treated there for injuries or panic.

In tiny Quillagua, with a population of around 100, one person suffered minor injuries and 15 houses were damaged.

Electricity was restored in large areas of Tocopilla. Army trucks were distributing water to residents as supply was still cut off in most of the city.

In Maria Elena, 1,200 homes were damaged — or 70% of the city’s total, authorities said. Residents were still without running water and electricity late yesterday.

Mr. Lagos Weber said about 170 people were taken to hospitals across the region, but that many of the injuries were not serious. About 10 road workers who had been trapped near Tocopilla when a section of a tunnel they were repairing collapsed were all rescued in good condition today.

Hundreds of residents slept in cars or tents in front of their houses. Schools were being used as shelters for those left homeless by the quake.

But officials said many are refusing to go to shelters, fearing their homes will be looted if left unattended.

“We slept in the car, because we have to care for whatever the quake didn’t destroy,” resident Luis Porcel said.