A powerful bomb shook central Beirut Friday morning, killing at least six people and injuring dozens more. Among the dead was Mohammed B. Chattah, a former Lebanese finance minister and ambassador to the United States who was a vocal critic of the government in neighboring Syria and its ally, the Lebanese militia and political party Hezbollah.

It was not immediately clear whether Mr. Chattah was the intended target of the car bomb, nor was there an immediate claim of responsibility for the attack, which was reminiscent of a string of unsolved bombings that have targeted anti-Syrian politicians over the past decade.

Mr. Chattah was a prominent member of the Future bloc, the mainly Sunni party headed by Saad Hariri, the son of the former prime minister Rafik Hariri, whose death in a 2005 bombing in Beirut sparked a protest movement that ended Syria’s 29-year military presence in Lebanon. […]