At least 13 people on the ground, including three children, were killed when a Mexican military helicopter carrying senior officials surveying damage from an earthquake crashed in the southern state of Oaxaca, authorities said on Saturday.
The aircraft, which was carrying Mexico's interior minister and the state governor, crashed on top of two vans in an open field while trying to land in the small town of Santiago Jamiltepec.
The senior officials survived but 12 people at the scene were killed and another died later in a hospital, said the Oaxaca Attorney General's Office. Fifteen more people were injured.
A 7.2 magnitude earthquake shook southern and central Mexico on Friday, causing panic less than six months after two devastating earthquakes that killed hundreds of people.
It left nearly a million homes and businesses without power in Mexico City and the south and damaged at least 50 homes in Oaxaca, where the epicentre was located.
The tremor triggered Mexico City's alarm system and caused buildings to sway in the capital, Agence France-Presse reported. It was also felt in the states of Guerrero, Puebla and Michoacan.
Panicked residents flooded into the streets, fearing a repeat of the two earthquakes last September, which caused buildings to collapse and killed a total of 465 people.
"To be honest, we're all pretty upset. We start crying whenever the [earthquake] alarm goes off," 38-year-old publicist Kevin Valladolid said after evacuating from his building in La Roma, in central Mexico City.
"We're stressed out, we have flashbacks. So we run out into the street. It's all we can do."
On the north side of the city, Julia Hernandez said she felt like she was "in a boat" as the ground swayed beneath her feet.
"Is it ever going to stop?" she said.
Standing in the middle of the street, her eyes glued to her fifth-floor apartment, Graciela Escalante, 72, could hardly speak.
"It was terribly strong. We barely managed to get down the stairs. It was the longest staircase in the world," she said.
"We thought everything was going to collapse again."
Officials in affected states said they were inspecting buildings damaged by last year's earthquakes, which are especially vulnerable to collapse.
"Obviously people are afraid," said the emergency response chief for the city of Puebla, Gustavo Ariza.
President Enrique Pena Nieto tweeted that the National Emergency Committee had been activated because of the magnitude of the latest tremor.
Emergency management authorities said there were no reports of major damage so far.
In Oaxaca, where the epicentre was located, authorities reported some structural damage to buildings in two towns, Pinotepa Nacional and Santiago Jamiltepec.
"Shelters have already been opened for those affected," the state government said on Twitter.
Mexico City mayor Miguel Angel Mancera reported "very minor" damage in the capital.
That included reports of a wall that collapsed in the upscale Condesa neighbourhood, which was hit hard by last year's earthquakes.
A nearby hospital evacuated patients into the street, some in wheelchairs or carting their IV lines. Similar scenes played out in Veracruz.
Meanwhile, Mexican interior minister Alfonso Navarrete told on Friday how was on board the helicopter that crashed near the epicentre of the earthquake.
"I understand that there are people who have lost their lives," Mr Navarrete told the Televisa network.
The interior minister tweeted that "two people who were on the land lost their lives in this incident".
He said the pilot of the military helicopter, which had flown from Mexico City to Pinotepa de Don Luis, about 37 kilometres southwest of the epicentre, lost control of the aircraft at a height of about 40 metres as it was coming in to land.
A Televisa reporter who was on board said the helicopter suddenly dropped after generating a large cloud of dust on its landing field.
TV images showed the downed aircraft lying on its side surrounded by several cars.
Mexican president Enrique Pena Nieto tweeted: "Unfortunately, several people on the ground lost their lives and others were injured. My condolences to your relatives and my desire to promptly recover the injured."