[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/08/23/art.mullensit0823.cnn.jpg caption="Admiral Mullen expressed concern Sunday about recent violence in Iraq."]
WASHINGTON (CNN) - The bloody attacks in Iraq last week have raised concerns over a renewal sectarian violence, the chairman of the U.S. Joint Chiefs of Staff said on Sunday.
Interviewed on CNN's "State of the Union," Adm. Mike Mullen said he is "extremely concerned" about recent bombings. More than 100 people were killed and more than 500 wounded in a series of truck bombings in Baghdad on August 19.
It was was the deadliest day since the United States pulled its combat troops from Iraqi cities and towns nearly two months ago and left security in the hands of the Iraqis. And it raised fears of a renewal of destabilizing Sunni-Shiite violence that raged a few years ago in Iraq.
"The key is whether this is an indicator of future sectarian violence," Mullen said. "And certainly, many of us believe that one way that this can come unwound is through sectarian violence."
Mullen said U.S. and Iraqi leadership is "focused" on dealing with such violence.
"We have not seen a lot of this really until last week. And we've seen some positive signs up north, where possibilities existed before, but it's something we're all very, very mindful of and watching very carefully," he said.
Meanwhile, the U.S. military reported the death of a U.S. soldier on Sunday in Baghdad, where he succumbed from combat-related injuries while conducting a patrol, the U.S. military said.