AYBAK, Afghanistan — A suicide bomber set off explosives after wading into a crowd of dignitaries at a wedding on Saturday in northern Afghanistan, killing at least 19 people, including a prominent Afghan lawmaker who was celebrating the marriage of his daughter, Afghan officials said.

Leaders from the smaller ethnic groups that dominate Afghanistan’s north have repeatedly been singled out for violent attacks in recent years, and the assassinations have fueled concerns that Afghanistan could splinter along ethnic lines as the American-led coalition pulls back in coming years.

The lawmaker, Ahmad Khan Samangani — the likely target of Saturday’s bombing — was a leading member of Afghanistan’s Uzbek ethnic group. He first rose to prominence fighting the Soviet Union during its occupation of Afghanistan in the 1980s; he then fought the Taliban in the 1990s. He was elected to Parliament last year from Samangan Province, where the attack took place.

The dead included at least five other former commanders from the old Northern Alliance, a loose confederation of Afghanistan’s smaller ethnic groups — Tajiks, Uzbeks and Hazaras — that in the 1990s fought the Taliban, which is almost entirely composed of ethnic Pashtuns from the south and east.