The death toll from a magnitude 6.3 earthquake in western Afghanistan on Saturday has risen to "about 120", disaster relief authorities said, with more than 1,000 others being treated for injuries.

The United States Geological Survey said the epicentre was 40 kilometres (25 miles) northwest of the region's largest city Herat, and was followed by eight aftershocks with magnitudes between 4.3 and 6.3.

"So far, more than 1,000 injured women, children, and old citizens have been included in our records, and about 120 people have lost their lives," Herat province disaster management head Mosa Ashari said.