Kiwis living in Mexico have described stumbling out of their buildings into plumes of dust and ash after a deadly 7.1 magnitude quake hit Mexico City and surrounding states yesterday.

At least 226 people died when the quake hit in the Puebla region, including 20 children when a school building collapsed.

The powerful quake toppled 44 buildings, broke gas mains and sparked fires. No Kiwis were reported injured, but New Zealand's embassy is monitoring the situation, Minister of Foreign Affairs Gerry Brownlee said.

He sent sympathy and offered aid to Mexico's President Pena Nieto.

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"New Zealand understands only too well the devastation that is caused by earthquakes," Brownlee said. "Our thoughts are with the injured, the loved ones of those affected, and the emergency services staff."

It was the second powerful earthquake to strike Mexico this month. An 8.1 magnitude quake off the country's coast killed 90 people on September 8.

But Kiwi Jai Krishnan told Radio New Zealand this quake was more terrifying. The Wellington man, who lives in Mexico City, was in his second-floor apartment when the shaking began.

"Parts of buildings have collapsed, about 100m from where I live a building has come down on the corner, it probably was six or seven storeys, and it's down to about two storeys now. It's so saddening to see."

The noise of sirens and helicopters was all around him.

"There's smoke pouring out of other buildings across the city."

Kiwi Simon Pierre, who coaches Mexico's Sevens rugby team, was at his desk at the rugby federation when the building started shaking.

He shouted "temblor" - the Spanish word for earthquake - and rushed with workmates down two flights of stairs to the street.

"Even once we were on the street the ground was still moving and it felt slightly like we were on a boat with a bit of a sea swell," Pierre said.

Pierre is from Dunedin but his wife's family lives in Mexico. All are safe but his wife was stuck in gridlocked traffic returning from Santa Fe.

There were some unscrupulous individuals taking advantage of the fact that traffic was not moving and there were few police officers in the street, Pierre said. "These groups ... are assaulting people in their cars and stealing their personal belongings."

The quake came hours before two earthquakes jolted New Zealand in quick succession but a geologist said they were not related to the Mexico quake - or to each other.

A 5.8 magnitude earthquake struck 585km southwest of Invercargill at 1.43pm, and an hour later the Cook Strait was rattled by a 5.1 quake that struck 30km northeast of Seddon.

GNS seismologist Dr Anna Kaiser said a big quake changes stresses in the earth's crust and could trigger aftershocks nearby.

"That's not a mechanism that could explain the earthquake in the Cook Strait because it was too far away," she said.