BAGHDAD - A sectarian controversy over control of a holy religious shrine where a 2006 bombing set off waves of sectarian killings turned violent again Monday, when a suicide car bomber struck a Shi’ite religious office in Baghdad, leaving at least 23 dead and more than 70 wounded.

The strike against the Shi’ite office was the deadliest single attack in the capital in nearly three months. It occurred as a dispute escalated between Sunnis and Shi’ites over control of the Askariya Shrine in Samarra, a largely Sunni city north of Baghdad.

Later Monday, an improvised explosive device was discovered in the rear of the Sunni Endowment office in Adhamiya, a Sunni stronghold, and was detonated under the supervision of security officials.

The Shi’ite and Sunni endowment offices, which administer mosques and other religious and cultural sites around the country, are the competing authorities at the center of the dispute over the shrine.

“Iraqis need to stop killing each other,’’ said Sadeq al-Mousawi, who was nearby but unharmed when the suicide bomber struck. “What did the victims of today do to be killed? Sectarianism has no mercy against anyone, and there are groups of criminals and militias used by officials and politicians to achieve their specific agendas.’’

While violence in Iraq has moderated in recent months, in the wake of the US troop withdrawal, the nature of Monday’s attacks laid bare the sectarian disputes that still poison Iraqi society. Attacks on Shi’ite pilgrims are still common, and several days ago a series of explosions rocked Baghdad, killing at least 17, including more than a dozen in a single strike in a market in a predominantly Shi’ite neighborhood.

Some at the bombing scene Monday said they believed the government was behind the attack, a frequent sentiment expressed in the wake of violence by Iraqis who know too well that many of their elected officials have in the past been linked to militias.

At the Sunni Endowment in Adhamiya, where the roadside bomb was discovered, an employee complained that the Shi’ites “are trying to take everything from the Sunnis, and now they are taking our mosques, one by one.’’

The 2006 bombing of the Askariya Shrine escalated the cycle of sectarian violence and dragged Iraq deeper into civil war.