A few days after a violent earthquake in Mexico, an aftershock in the middle of the night claimed two more lives.

Mexico's President Andrés Manuel López Obrador said in a short video speech on Twitter early Thursday morning.

Two people died in a magnitude 7.7 earthquake on Monday.

The center of the most recent 6.9 magnitude tremor was on the Pacific coast in the state of Michoacán, according to the National Seismological Institute.

The US agency USGS gave the strength at 6.8.

The aftershock surprised people at 01:06 local time, when most were already asleep.

After Monday's earthquake, exactly on the anniversary of the strong earthquakes of 2017 and 1985, the Seismological Institute registered more than 1,200 aftershocks that were felt in several states.

Mexico and the entire west coast of South, Central and North America lie on the Pacific Ring of Fire.

This is the most geologically active region in the world.

90 percent of all earthquakes worldwide occur there.