BAGHDAD — More than 50 people were killed in a wave of car bombings on Monday that struck Shiite neighborhoods in Baghdad despite tightened security measures, officials and security forces said.

The attacks started during the afternoon rush hour. A car bomb exploded at a public market, killing six people, the police said. Just after that, eight car bombings hit Shiite neighborhoods, including Huriya, Sadr City, Baya, Zafaraniya and Kadhimiya.

Altogether, at least 53 people were killed in the attacks and more than 100 were wounded, yet another sign of a surge in violence as sectarian tensions have risen in the last month.

Recent bombing attacks have increased concerns that the violence is pushing the country toward the kind of widespread sectarian fighting it suffered in 2006 and 2007.