In the country's deadliest single attack since 2011, the bomber detonated his explosives yesterday as hundreds of young men and boys attended a tournament featuring three local teams in the volatile province of Paktika.
Separately, two NATO soldiers were killed in an attack in the east of Afghanistan this morning, the coalition said, giving no further details.
Paktika provincial spokesman Mukhlis Afghan said in a statement the death toll from yesterday's blast had risen to 57 after 15 people died of their injuries overnight.
"I was shouting for help. Just beside me was a dead army officer," he said. "There were local police and commanders watching the game. I saw some killed and wounded."
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Najib Danish, deputy spokesman for the interior ministry, said four local police were among the fatalities, but they did not appear to have been specially targeted.
The attack underlined the challenges facing President Ashraf Ghani, who came to power in September, as US-led NATO troops wind down operations and Afghan security forces take over full responsibility for fighting Taliban insurgents.
"People were covered in blood all around me. There were many friends of mine among them."
Many of the wounded were children or young men, wrapped in bloody bandages.
Doctor Seyawash, head of health services at the hospital in Kabul, told reporters that about 12 victims were in a critical condition. The injuries were from ball bearings packed in the bomb.
There was no immediate response from the Taliban, but the insurgents often distance themselves from attacks that claim many civilian lives.