Scientists report an extremely violent 8.4 magnitude earthquake has shaken the sea floor 165km west of Chiapas state a few minutes before midnight local time on Thursday.
A tsunami warning was issued immediately afterwards and residents in coastal towns evacuated to higher ground. The expected increase in wave activity is likely to be felt across the world as far away as Australia.
The first waves recorded at nearby Salina Cruz were close to a metre over the usual tide level.
More waves are predicted around a metre in size for the Cook Islands, Fiji, Polynesia, Guatemala and Kiribati in the middle of the Pacific Ocean.
Australia, Japan and Vietnam are expected to receive waves around 0.3m high.
The quake was so powerful that it was felt in Mexico City, more than 1,000km away.
Mexico is also experiencing the effects of Hurricane Katia, which is on the other side of the country in the Gulf of Mexico. Forecasters say Katia will move southwest towards the eastern coast of Mexico and bring torrential rains to Veracruz state.
That's as Hurricane Irma continues to move towards Florida in the US, while another tropical storm was upgraded to Hurricane status on Wednesday evening, Hurricane Jose.
Hurricane Harvey missed Mexico last week, and the country has sent rescue teams to assist people in Texas. After months of US President Donald Trump threatening to build a wall to stop Mexicans entering the US, people from Mexico are making the crossing to help their neighbour. Mexican volunteers wearing white vests labelled “Cruz Roja Mexicana” are in Texas and have helped around 1,800 refugees of Hurricane Harvey in Houston.
