KABUL, Afghanistan — A suicide bomber killed at least 57 people on Sunday as they lined up at a government office in Kabul to register to vote, raising new concerns about the potential for violence to undermine Afghanistan’s long-delayed parliamentary elections.

The attacker detonated his explosives as the Afghan authorities distributed national identity cards in the western part of Kabul, the capital, part of a push by the government to get more people to register to vote. Wahidullah Majrooh, a spokesman for the Afghan Health Ministry, said the attack also wounded at least 119 others.

Among the dead were 25 men, 22 women and eight children, while two bodies were not identifiable, Mr. Majrooh said.

Public interest in the October elections has been alarmingly low because of voter fatigue after successive fraudulent elections and concerns about the threat to safety at polling stations posed by suicide bombers and other violence from groups opposing the government.