Iraqi officials say two nearly simultaneous car bomb blasts in a central Baghdad market have killed at least 88 people and wounded more than 160 others.
The explosions Monday tore through stalls of vendors and left charred bodies strewn around the market in the Bab al-Sharqi area.
North of Baghdad, a bomb killed at least 12 people in a market near Baquba.
The blasts appeared to be part of a renewed campaign of Sunni insurgent violence against Shi'ite targets.
Meanwhile, the Iraq branch of al-Qaida is claiming it shot down a U.S. military helicopter north of Baghdad on Saturday.
In an Internet posting, the group said it also engaged with U.S. troops at the site, destroying two Humvees and killing the U.S. soldiers in them. The statement could not be independently verified.
U.S. officials, speaking anonymously, say insurgents may have launched a shoulder-fired missile at the helicopter.
The 12 U.S. troops on board the helicopter were killed.
Officially, the U.S. military says an investigation is still under way.
A surge in violence in recent days has coincided with the arrival of the first U.S. reinforcements sent as part of President Bush's controversial new security strategy.
The U.S. military also announced Monday that a roadside bombing killed a U.S. soldier in northern Nineveh province, while two Marines were killed in separate incidents in the western province of al-Anbar.
In an interview with the newspaper, "USA Today," Mr. Bush says he will not set a timetable for withdrawing troops from Iraq, because doing so would enable insurgents to adjust their tactics.