Helicopter crash only casualties from Mexico quake

A woman is helped outside, along Reforma Avenue after a 7.2-magnitude earthquake shook Mexico City. Photo / AP

A prolonged 7.2 magnitude quake that's rocked Mexico has left nearly a million homes and businesses without power in the capital and south, but the only reported deaths came when a military helicopter crashed after surveying the aftermath.

At least 50 homes suffered damage in the southern state of Oaxaca, which, along with Mexico City, is still reeling from earthquakes that caused widespread damage in September.

The epicentre was about 145km from Pacific coast surfer resort Puerto Escondido in the southern state of Oaxaca and had a depth of 24.6km, according to the US Geological Survey.

At least two people died when a helicopter carrying Mexico's interior minister and the governor of Oaxaca crashed while trying to land after a tour of damage from the earthquake, officials said.

The senior officials survived.

Friday's powerful, sustained shaking gave way to 225 aftershocks, the national seismology service said, and caused widespread panic.

In Mexico City, the seismic alarm sounded more than a minute before tremors were felt, Mayor Miguel Angel Mancera said, giving residents time to flee to the streets.

Patricia Gutierrez, a 66-year-old English teacher, was taking a nap with her 11-month-old granddaughter, Juliet, when she heard the distinctive siren.

She managed to leave her ground floor apartment before the quake began.

Authorities said no deaths directly linked to the quake had been reported nationally.

The Oaxacan town of Jamiltepec appeared to sustain the heaviest impact in the southern region, with 50 homes damaged along with a church and government building, the state's civil protection agency said.

Patients were evacuated from a hospital there and from another in the nearby town of Putla Villa de Guerrero.

About 100,000 people in Oaxaca had lost power, the state's governor said.

Tremors were felt as far away as Guatemala to the south.

The Popocatepetl volcano south of the capital sent a kilometre-high column of ash into the sky, Mexico's disaster prevention agency said.

- AP