School collapse during Mexico earthquake kills 22 children

The death toll from the Mexico earthquake has risen to 216, including 22 children found after their school collapsed.

Thirty other children and 12 teachers are still missing after the powerful earthquake, which registed at 7.1 magnitude.

That toll is expected to rise as rescue teams search through the rubble of collapsed buildings.

The rescue operation gets underway. Source: AAP

The earthquake struck on the 32nd anniversary of a massive earthquake that killed thousands in the capital.

The state of Morelos, just south of Mexico City, was also hard hit with 55 killed.

At least 12 people were killed in the neighbouring state of Mexico, and three deaths were reported in the state of Guerrero on the Pacific coast.

The quake toppled dozens of buildings, broke gas mains and sparked fires less than two weeks after another powerful quake killed at least 98 people in southern Mexico.

A man is pulled from the rubble after the 7.1 magnitude quake. Source: AAP

It also hit just hours after emergency drills marked the anniversary of a quake that killed thousands in 1985.

Millions of people fled into the streets, where they weathered the violent shaking and desperately sought word about the welfare of family and friends.

A car is buried under rubble. Source: 7 News

Emergency personnel in Mexico City, a metropolitan region of about 20 million people, searched frantically with picks and shovels for survivors beneath the rubble of what the sprawling city's mayor calculated to be as many as 44 collapsed buildings, including at least one primary school.

Mexican President Enrique Pena Nieto said more than 20 children and two adults had been found dead at the school, Colegio Enrique Rebsamen, in the neighbourhood of Coapa.

Rescue teams search through collapsed buildings. Source: AAP

Emergency personnel and equipment were being deployed across affected areas so that "throughout the night we can continue aiding the population and eventually find people beneath the rubble," Pena Nieto said in a video posted on Facebook.

Rescue workers and soldiers toiled around collapsed buildings where heat-sensing equipment suggested survivors could still be trapped. Bystanders joined in where they could, clearing debris with their bare hands or whatever tools they could find nearby.

The earthquake hit central Mexico. Source: 7 News

As many as 4.6 million homes, businesses and other facilities had lost electricity, according to national power company Comision Federal de Electricidad. Most of them were in the greater Mexico City area and in the states of Guerrero, Morelos, Puebla, Oaxaca, and Tlaxcala.

In the capital, ambulances and fire engines confronted gridlock as millions of workers tried to get home, many of them after participating in annual readiness drills that commemorate the previous disaster on this date in 1985.

A scene of devastation. Source: AAP

Leaders have sent messages of support to Mexico.

US President Donald Trump, who has courted controversy with his plans for a border wall with Mexico, tweeted: "God bless the people of Mexico City. We are with you and will be there for you."

Canadian Prime Minister Justin Trudeau also tweeted his support following the "devastating news".