(Mexican President Enrique Pena Nieto (C) inspects the rescue work in Jojutla, state of Morelos, Mexico, on Sept. 20, 2017. Mexico's President Enrique Pena Nieto decreed three days of national mourning on Wednesday for the victims of the powerful quake that killed over 200 people and toppled buildings in central Mexico on Tuesday. Xinhua/Armando Solis)

Mexico's President Enrique Pena Nieto decreed three days of national mourning on Wednesday for the victims of the powerful quake that killed over 200 people and toppled buildings in central Mexico on Tuesday.

The office of the presidency made the announcement on Twitter, saying it was "to honor" the more than 200 known fatal victims of the 7.1-magnitude quake.

Previously, Pena Nieto announced three days of national mourning for the victims of the 8.2-magnitude quake that hit southern Mexico on Sept. 7, killing nearly 100 people, mainly in the states of Chiapas and Oaxaca.

The death toll from Tuesday's quake is gradually rising as rescue workers in the capital Mexico City, where 38 buildings collapsed, retrieve bodies from the rubble, and authorities assess damage in surrounding states, including Morelos, Puebla and Mexico State.

Mexico City authorities said 93 people have been confirmed dead in the capital.

"That is the official figure that we have," Mayor Miguel Angel Mancera told reporters at a press conference.

Some 52 survivors have been rescued from the rubble, he said.

Many city hospitals are providing treatment free of charge to the injured, and the subway system is free to encourage people to leave their cars at home, freeing up the roads for emergency vehicles, and allow volunteers to get about easily.

The head of the national civil protection agency, Luis Felipe Puente, adjusted the total number of deaths at 223 on Wednesday afternoon.

The first quake was reported to be the strongest to hit Mexico in nearly 100 years, and the second, the strongest to hit Mexico City in 30 years.

Tuesday's quake struck on the 32nd anniversary of a devastating 1985 temblor that killed thousands in Mexico City.

According to scientists, the country sits above five active tectonic plates, making it highly quake prone.