As the closest large metropolitan area to the epicenter, the historic city of Marrakesh was among the most affected cities, according to local media, although the shock was also felt in other cities, including in Casablanca, Rabat, and Fez.

The quake has sparked concern about landmarks that may have been damaged, particularly Marrakesh’s medina, a UNESCO World Heritage site known for its bustling markets, tight streets, monumental Islamic architecture and perimeter of pink walls.

Residents of Marrakesh said buildings had collapsed within the old city, Reuters reported. Social media users expressed worry that the Kutubiyya mosque, described as “an essential monument of Muslim architecture” by UNESCO, may have been affected by the shaking.

The earthquake struck in the Morocco’s Atlas Mountains, near Toubkal, the highest peak in North Africa. The epicenter was only about 11 miles under the Earth’s surface, according to the United States Geological Survey. Shallow earthquakes tend to be more destructive.

The USGS said in a preliminary report that 49,000 people are estimated to have experienced “severe” exposure to the quake, while 403,000 are believed to have experienced “very strong” exposure. “Significant casualties are likely” and extensive economic loses are “probable,” the organization said.

According to the USGS, since 1900, there have been no magnitude 6 or larger earthquakes within 310 miles (500 kilometers) of where Friday’s event occurred in the Atlas mountains, and only nine earthquakes of magnitude 5 or higher.

“Earthquakes of this size in the region are uncommon but not unexpected,” a statement said. The organization also wrote that the population in the affected region “resides in structures that are highly vulnerable to earthquake shaking.”

Nacer Jabour, a representative of Morocco’s National Institute of Geophysics, told Moroccan media that the main shock was “followed by hundreds of aftershocks”

He added that this is the first time in a century that they had recorded this level of seismic activity in Morocco.

Several world leaders, including Indian Prime Minister Narendra Modi and German Chancellor Olaf Scholz, expressed their sympathies to those affected in Morocco.

This is a developing story and will be updated.