Update 3.12pm: A strong new earthquake has shaken Mexico as the country reels from two more-powerful quakes this month that have killed nearly 400 people.
The new magnitude 6.1 earthquake was centered about 11 miles (18km) south-southeast of Matias Romero in the state of Oaxaca, the US Geological Survey said.
That was the region most battered by a magnitude 8.1 quake on September 7.
It swayed buildings and set off a seismic alarm in the capital, prompting civil defence officials to temporarily suspend rescue operations in the rubble of buildings downed by Thursday's magnitude 7.1 quake in central Mexico.
Quake alarms sounded in Mexico City as the new quake struck, prompting people with fresh memories of this week's devastating tremor to flee homes and hotels.
Alejandra Castellanos was on the second floor of a hotel in a central area and ran down the stairs and outside with her husband.
She said: "I was frightened because I thought, not again!"
At the site of an office that collapsed on Tuesday, street signs swayed and rescuers briefly evacuated from atop the pile of rubble before returning to work.
Nataniel Hernandez lives in Tonala, one of the cities hardest hit by an earlier, September 7 quake, which struck off the coast of southern Mexico with a magnitude of 8.1.
He said by phone that it was one of the strongest movements he has felt since then.
But he added: "Since Septemer 7 it has not stopped shaking."
Earlier: A new earthquake to strike Mexico had a magnitude of 6.2 and was centered in the southern state of Oaxaca, the US Geological Survey says.
It also swayed buildings in Mexico City, which is trying to recover from a magnitude 7.1 temblor that struck on Tuesday, killing at least 295 people.
A magnitude 8.1 earthquake also struck earlier this month near the state of Chiapas.