ISLAMABAD, Pakistan — A bombing killed at least 20 people on Saturday during an auction at a vegetable market in a mostly Shiite town in northwestern Pakistan, ending a long lull in militant violence there, officials said.

At least 43 people were wounded in the morning bombing in Parachinar, capital of the Kurram tribal region, which borders Afghanistan. The Pakistani Taliban claimed responsibility for the attack.

“I was in my shop when a deafening blast shook the market,” a Parachinar resident, Hussain Ali Tori, said by telephone. “I have seen dozens of shattered bodies lying on the ground. Some were dead, and many were crying for help.”

A Taliban spokesman, Muhammad Khurasani, said a suicide bomber had carried out the attack, but a Kurram official, Nasrullah Khan, said the bomb appeared to have been planted in a crate. “The place is always crowded,” said Mr. Khan, a deputy administrator.