At least 59 people were killed in two countries after one of the strongest earthquakes to hit Turkey in more than 100 years sent tremors across the region, collapsing buildings and sending residents running into the streets, CNN reported.

The 7.8-magnitude quake struck 23 kilometers (14.2 miles) east of Nurdagi, Gaziantep province at a depth of 24.1 kilometers (14.9 miles), the United States Geological Survey (USGS) said. Nurdagi is located along the Turkey-Syria border and the quake was felt in several countries across the region, including Syria and Lebanon.

At least 17 people were killed in Turkey, according to local officials, while in neighboring Syria, at least 42 people died and around 200 more were injured, Syrian state run news agency SANA reported, citing a health ministry official.

In Syria, the deaths were reported in Aleppo, Hama and Latakia, SANA said. Dozens of people are trapped under rubble, according to the “White Helmets” group, officially known as Syria Civil Defense, according to CNN.

The quake struck while residents were likely asleep and unprepared for the impact. Video shared on social media show dozens of collapsed buildings, while frightened residents huddled on the darkened streets amid the chaos. Rescue workers can be seen conducting search-and-rescue operations by flashlight.

Monday’s quake is believed to be the strongest to hit Turkey since 1939, when an earthquake of the same magnitude killed 30,000 people, according to the USGS. Earthquakes of this magnitude are rare, with fewer than five occurring each year on average, anywhere in the world. Seven quakes with magnitude 7.0 or greater have struck Turkey in the past 25 years – but Monday’s is the most powerful.

Karl Lang, an assistant professor at Georgia Tech University’s School of Earth and Atmospheric Sciences, told CNN the area hit by the quake Monday is prone to seismic activity. “It’s a very large fault zone, but this is a larger earthquake than they’ve experienced any time in recent memory,” Lang said