BAGHDAD, Iraq — A roadside bomb exploded in Baghdad's oldest and largest wholesale market district, killing at least 24 people and wounding 35, part of a surge in bloodshed today that left 52 dead, authorities said.

Earlier, an explosives-rigged bicycle blew up near an army recruiting center in a city south of Baghdad, killing at least 12 people.

Violence across Iraq has spiked in recent days, with more than 200 people killed since Sunday in clashes, bombings or shootings — despite U.S. and Iraqi officials' claims that a new security operation in the capital has lowered Sunni-Shiite killing there.

A U.S. Marine from the 1st Brigade of the 1st Armored Division was also killed in action Tuesday in Anbar province, the U.S. command said.

The market bomb in Baghdad targeted the Shurja district, where wholesalers use warehouses, stalls and shops to sell food, clothing and house products to other dealers and shoppers.

Elsewhere in Baghdad, a Justice Ministry official, Nadiya Mohammed Hassan, was shot and killed along with her driver and bodyguard by gunmen who stopped her car. Three carpet merchants were also killed while being driven to an appointment in a taxi, police said. A family of five was killed in Buhriz, 35 miles north of Baghdad, when a roadside bomb struck their car.

In downtown Baghdad, three police officers were killed and 14 people were injured when twin bombs — including one planted in a car — struck a police patrol as it drove by a line of vehicles waiting in a line for gasoline at a filling station.

An explosion Tuesday at an oil pipeline near the city of Diwaniyah, south of Baghdad, caused a massive fire that left at least 36 people dead and 45 injured, the Interior Ministry said. The city's health directorate said another 40 people were still missing.

The cause of the blast was not clear, but police Lt. Raid Jabir said several people had been siphoning fuel from the pipeline at the time.

In other violence Wednesday, according to police:

• An Iraqi army major was killed in Kut, 100 miles southeast of Baghdad, by a roadside bomb.

• A civilian driving in his car in northern Mosul was apparently shot and killed by American troops who opened fire when the man's vehicle came too close to them.

• Five bullet-riddled bodies turned up in Suwayrah, 25 miles south of Baghdad.