A magnitude 6.3 earthquake hit western Afghanistan on Saturday morning, the United States Geological Survey said, followed by four large aftershocks with epicentres close to the region's largest city.
The USGS said the epicentre was 40 kilometres (25 miles) northwest of the city of Herat, and was quickly followed by aftershocks with magnitudes of 5.5, 4.7, 6.3 and 5.9.
15 people have been killed, with the death toll expected to reach higher numbers.
An AFP journalist in the city said residents and shopkeepers fled buildings when the first quake hit around 11:00 am (0630 GMT), but that there were not yet reports of casualties.
"We were in our offices and suddenly the building started shaking, and wall plasters started to fall down and the walls got cracks, some walls and parts of the building collapsed," 45-year-old Bashir Ahmad told AFP.
"I am not able to contact my family, network connections are disconnected. I am too worried and scared, it was horrifying," he said.
Crowds of women and children stood out in the wide streets of Herat, away from tall buildings, in the moments after the first quake and aftershocks which continued for roughly one hour.
Hundreds of fatalities were possible, according to a USGS preliminary report.
"Significant casualties are likely and the disaster is potentially widespread. Past events with this alert level have required a regional or national level response," it said.
Taliban government disaster management officials could not immediately be reached for comment.
USGS had earlier reported the first quake's magnitude as 6.2. It had a shallow depth of just 14 kilometres, it said.
Herat - 120 kilometres east of the border with Iran - is considered the cultural capital of Afghanistan.
It is the capital of Herat province which is home to an estimated population of 1.9 million, according to 2019 World Bank data.
In June last year, more than 1,000 people were killed and tens of thousands made homeless after a 5.9-magnitude quake - the deadliest in Afghanistan in nearly a quarter of a century - struck the impoverished province of Paktika.
In March of this year, 13 people were killed in Afghanistan and Pakistan by a magnitude 6.5 quake, which hit near Jurm in northeastern Afghanistan.
The country is frequently hit by earthquakes, especially in the Hindu Kush mountain range, which lies near the junction of the Eurasian and Indian tectonic plates.
Afghanistan is already in the grip of a grinding humanitarian crisis, with the widespread withdrawal of foreign aid since the Taliban returned to power in 2021.