Iraqi officials say more than 50 bodies have been found in Baghdad over the past day.
The U.S. military also says a mass grave with 28 bodies has been found near the troubled city of Baquba, north of Baghdad.
In other violence, the deputy of a local Sunni Endowment office, Nasir Gatami, and three of his bodyguards were killed in the southern city of Basra in an ambush on their two-car convoy. The Sunni Endowment office is a government agency that cares for Sunni mosques and shrines nationwide.
As violence continued across the country, Prime Minister Nouri al- Maliki returned to Baghdad to face new political troubles.
Criticism of the Maliki government by coalition partners is spreading, with some Sunni leaders in parliament calling for a boycott.
Vice President Tariq al-Hashemi, a Sunni Arab, told the Associated Press that he wants to see Mr. Maliki's government gone and a new coalition put in place.
On Wednesday, 30 lawmakers loyal to the radical Shi'ite cleric Moqtada al-Sadr suspended their participation in Iraq's government.
They bolted in protest over Mr. Maliki's meeting with President Bush in Amman.
The United States said Wednesday it is moving about two thousand troops from northern Iraq to Baghdad to help stabilize the security situation.
The U.S. military also announced the deaths of two American soldiers from combat operations Wednesday and Thursday in Baghdad.
Some information for this report was provided by AFP, AP and Reuters.