Heavy seasonal rains have set off flash floods across Afghanistan, killing at least 137 people in one province, leaving at least 100 more missing and displacing thousands of others this weekend, officials said.

The flood’s toll in the northern province of Baghlan, which appeared to have suffered the worst devastation, was likely to rise, said Hedayatullah Hamdard, the director of the provincial disaster management department. Most of the dead there were women and children, he said.

Flooding began around 4 p.m. Friday and continued into the evening in Baghlan Province. Abdul Aziz Ayyar, a tribal elder, was in his home in the Baghlan-e-Markazi District when rain began pouring down. He stepped outside and saw a torrent of water rushing down a nearby mountain toward his village.

He grabbed his two children and wife and began sprinting to a different nearby mountain, shouting as he ran to warn the other villagers, he said. His 30-year-old niece was running behind him, carrying her 1-year-old and 3-year-old daughters. At one point, his niece tried to grab his hand to steady her and her children, he said, but before he could grab her, floodwater crashed over them, carrying them away.

“We returned to the village after midnight to save people, but they were all dead,” Mr. Ayyar said on Saturday. “Everything was flooded. There are three villages in our area where no houses are left; all have been razed by the flood.”

Flooding also killed at least one person in Badakhshan, a mountainous eastern province, where homes, small dams and bridges were destroyed and 2,000 livestock were killed, the provincial diaster management department said.