KABUL, Afghanistan — A suicide bomber struck a crowd of Shiite worshippers who packed a Kabul mosque Tuesday to mark a holy day, killing at least 56 people, and a second bombing in another city killed four more Shiites. The were the first major sectarian assaults since the fall of the Taliban a decade ago.

A third attack, a motorcycle bomb in the southern city of Kandahar, killed one civilian. But police said it did not target Shiites as they commemorated Ashoura, which marks the seventh century death of the Prophet Muhammad’s grandson Imam Hussein.