text: Many of the dead were young boys who were in a trophy ceremony hit by the bomber, himself said to be a teenager.
  So-called Islamic State (IS) said it carried out the attack.
  IS is a mainly Sunni group which controls large swathes of northern and western Iraq, and has attacked numerous Shia targets in the country.
  UN Secretary General Ban Ki-moon, in Iraq for talks with the government, expressed his condolences to the families of the victims.
  "I would like to take this opportunity to express my deepest condolences to the people and government of Iraq, and particularly those members of the families affected by terrorist attacks yesterday," he told reporters in Baghdad.
  Mr Ban urged Iraqi leaders to step up reconciliation efforts between Shias and Sunnis in order to defeat IS.
  Friday's attack happened in Iskandariya, a mainly Shia town 40km (25 miles) south of the capital, Baghdad.
  Video posted on social media showed the moment of the blast, as an official was speaking in front of a crowd of dozens of people, including the young players.
  The footage cuts off with a big flash of yellow light. It then shows the chaos and screaming of people fleeing the area.
  A medical official said 17 of the dead were boys aged between 10 and 16, AFP news agency reported.
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  Mayor Ahmed Shaker was also killed, as was one of his bodyguards and at least five members of the security forces, it said.
  Some 84 others were wounded, and 12 of them were said to be in critical condition.
  Iskandariya is in a region that was once called "the triangle of death" and was badly affected by sectarian violence that followed the 2003 US-led invasion of Iraq.
  In a statement, FIFA President Gianni Infantino said he was "shocked" by what he described as a "tragedy".
  The UN chief also urged politicians to foster reconciliation with the minority Sunni, who say they were marginalised under the Shia-led government.
  Some discontented Sunnis have joined IS and other extremist groups.
  "National reconciliation is an important part of the strategy to defeat Daesh, who have ruthlessly exploited divisions and targeted the marginalized and disenfranchised," he said, using another name for IS.
  IS has been losing some territory of its self-declared caliphate that includes parts of neighbouring Syria, and Iraqi forces have started an operation to retake Mosul, the largest city under the group's control.
  Meanwhile, thousands of supporters of the powerful Shia cleric Moqtada Sadr continued their sit-in outside the gates of the heavily fortified Green Zone, an area of government offices and embassies in Baghdad.
  They have urged Prime Minister Haider al-Abadi to announce a new-cabinet and fresh measures to fight corruption.
  Mr Abadi said on Saturday a new cabinet would be announced within a week.
target: Iraq has buried the victims of a suicide attack in a football match in the city of Iskandariya that killed at least 32 people.