Story highlights At least 125 others are wounded in six car bombings and three roadside bombs

Police: The blasts mainly targeted Shiite neighborhoods

Overall violence in Iraq has dropped in recent years

But recent violence spurs fears of renewed sectarian warfare

A spate of bombs exploded in Baghdad on Sunday, killing at least 21 people and wounding 125 others, police said.

The blasts -- six car bombs and three roadside explosions -- mainly targeted outdoor markets in Shiite neighborhoods, Baghdad police said.

Overall violence has dropped significantly in Iraq since the peak of sectarian violence, between 2005 and 2007. Yet such attacks continue as the 10-year anniversary of the U.S-led invasion of Iraq nears next month.

The U.S. Embassy in Baghdad condemned the attacks.

Recent attacks in Shiite areas have spread fear among Iraqis that sectarian warfare may ravage the country again.

Sunnis demand that the Shiite-led government stop what they call second-class treatment of Iraq's Sunni community.

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Sunnis largely boycotted Iraq's 2005 elections, leading to the emergence of a Shiite-led government. The move left the once-ruling minority disaffected.

Last month, at least 177 Iraqi civilians, soldiers and police officers were killed in attacks, according to figures compiled by Iraq's interior, defense and health ministries.

The casualties were predominantly civilians, according to the ministries.

The total does not include those killed in Iraq's semi-autonomous Kurdish region, which keeps its own death toll.

Security has deteriorated since last December, when Sunni demonstrators in provinces such as Anbar and Mosul called for an end to what they considered second-class treatment.

The protests were triggered when Iraqi security forces arrested several bodyguards of Finance Minister Rafie al-Essawi, a Sunni.