A car bombing outside a Shi'ite mosque in northern Iraq killed at least 15 people and wounded more than 26 others Wednesday.
Iraqi officials said the blast occurred in the city of Baquba, the capital of Diyala province.
News organizations quoted unidentified government officials in the region as saying the death toll may be as high as 30.
There was no immediate claim of responsibility for the attack, which was the third assault in or near Baquba since Monday.
Also Wednesday, a U.S. soldier was killed after his vehicle hit a roadside bomb in Diyala province.
Meanwhile, the top U.S. military commander in Iraq says the U.S. troop withdrawal from Iraq is on schedule, despite the recent wave of violence there.
General Ray Odierno told reporters in Washington Wednesday, the number of American troops in Iraq will decrease to 50,000 by September 1, from the current level of about 70,000.
Odierno said it is likely that the U.S. will maintain the 50,000-troop level through the summer of 2011. He added that the U.S. is also on schedule with its plans to fully withdraw by the end of 2011.
Some information for this report was provided by AP and Reuters.