A suicide bomber has killed at least 45 people at a volleyball tournament in eastern Afghanistan, officials say.
A spokesman for the governor of Paktika province told the BBC that the attacker had detonated the bomb amid a crowd of people gathering for a game.
About 60 people were also wounded in the bombing in Yahyakhail district.
It came after Afghan MPs approved security deals allowing Nato and US soldiers to remain after the withdrawal of most foreign troops next month.
The total number of soldiers in the new Nato force will be about 12,000. Their mission has been defined as training, advising and assisting the Afghan security forces.
There will also be a separate US-led force dealing with the remnants of al-Qaeda.
It emerged on Saturday, however, that President Barack Obama has approved guidelines to allow US troops to fight the Taliban and provide air support for Afghan missions.
Sunday's bombing occurred when a crowd of people were preparing to watch the final of a regional volleyball tournament.
Local reports say a suicide bomber walked into the large gathering before detonating the explosives.
A spokesman for the provincial governor told the BBC that the crowd was made up mostly of young people. He said all of the casualties were civilians.
The dead and injured have been taken to a local hospital, he added, but said the governor has requested that helicopters be sent from Kabul to take the most seriously injured for treatment in the capital.
The BBC's Richard Galpin, who is in Kabul, says a doctor at the local hospital was crying as he spoke of treating many wounded children.
He said several people had died on the journey to the hospital.
President Ashraf Ghani, who came to power in September, described the incident as a "heinous attack", according to his spokesman.
The Taliban have stepped up attacks on both Western and Afghan targets across the country this year.
The agreements with Nato and the US still need to be ratified by the Afghan upper house.