The horror quake, which was felt as far as Mexico City and Guatemala City, was registered off Mexico's southern coast just as heavy rains from Hurricane Katia lashed the east.

It emerged today that at least 90 have been killed.

The epicentre was in the Pacific Ocean, some 600 miles southeast of the capital and 74 miles from the Pacific coast.

The state of Oaxaca took the brunt of the damage, 20 deaths have been reported there, while other casualties were from the Tabasco area.

A tsunami warning was then issued off the Mexican coast – but the expected wave didn't strike.

**MAPPED: Where tsunamis were expected to strike after killer mega earthquake**

Mexico City was thrown into chaos with desperate residents fleeing their homes.

Residents took to Twitter to describe their homes shaking.

Widespread power cuts were reported with extensive damage.

The Mexican capital was struck by an 8.0 magnitude earthquake in 1985, which killed about 5,000 people and razed buildings to the ground.

People on the coast of Oaxaca and Chiapas were told to prepare for an evacuation ahead of a possible tsunami.

The quake's epicentre was 123 km (76 miles) southwest of the town of Pijijiapan and at a depth of 33 km (21 miles).

Thousands of people have taken to Twitter to describe their terror.

One person wrote: "I almost s*** my pants... I've never felt an earthquake that intense."

Another said their life flashed before their eyes.

Those with family members in the country also reported being unable to contact them with phone lines down.

One desperate woman tweeted: "Hoping my everyone and my family is okay, currently calls aren't going through."

People as far as the United States even claimed they felt tremors, with Texas residents saying they felt the shaking.

Mexico's civil protection agency said it was the strongest earthquake to hit the country since a devastating 1985 tremor that toppled buildings and killed thousands.

Luis Carlos Briceno, an architect, 31, who was visiting Mexico City, said: "I had never been anywhere where the earth moved so much.

"At first, I laughed, but when the lights went out I didn't know what to do. I nearly fell over."