BEIRUT – Lebanese protesters erected flaming roadblocks and gunmen roamed the streets Saturday in a city on edge after the assassination of a top security official in a powerful car bomb the prime minister linked to the civil war in neighboring Syria.

The crisis raised a terrifying specter for Lebanese who fear their country could easily plunge back into cycles of violence and reprisal that have haunted it for decades.

Friday’s blast in the heart of Beirut’s Christian area killed eight people, including the country’s intelligence chief, Brig. Gen. Wissam al-Hassan. It was the deadliest bombing in Beirut in four years, shattering the country’s uneasy calm.