At least 26 people were killed and 190 others were wounded as a suicide attacker blew up a bomb-packed car at a Shiite religious foundation's headquarters in Bab al-Muazzam in central Baghdad on Monday, Reuters reported, with references to the local police and medical workers.
Two policemen were among the victims, the Associated Press reported.
Shiite Prime Minister Nouri al-Maliki and President of Parliament, the Sunni Osama al-Noujaifi, condemned the attack and called for calm.
The building was "totally destroyed," deputy director of the foundation, Sheikh Sami al-Massoudi said, stressing that "martyrs are buried under the ruins," AFP news reported.
At the scene of the attack, dozens of ambulances and rescue workers were trying to evacuate the wounded and search the rubble, while relatives gathered nearby.
Mohamed, owner of a restaurant opposite to the targeted site, crying, said: "It was a 4X4 white, he (the bomber) was going too fast and struck the door of the foundation and exploded. Suddenly I saw two of my employees dead before me," he added.
Iraq has been facing for six months a severe political crisis between Maliki and Kurdish and several Sunni leaders who criticize his "authoritarianism." The tone has hardened in recent weeks and the radical Shiite cleric Moqtada Sadr and the secular Iraqiya bloc have called in recent days to Maliki to resign.
However, according a joint report Issued by ministry of internal affairs and the ministry of health in Iraq, the number of Iraqis killed in terrorist attacks in various cities of the country has grown for the third consecutive month.
In May, 132 people were killed in acts of terror, including 90 civilians, 20 policemen, and 22 soldiers.
In April, the total number was 126 while in March it was 112.
The largest terrorist attack in May was a series of blasts in Baghdad on May 31. As a result, 17 people were killed.