A suicide bomber killed more than 80 people at a picnic spot in the southern Afghan province of Kandahar.
The attack, in which at least 50 people were wounded, happened in a field where a crowd of people including police were watching dog fights in Arghandab, on the western outskirts of Kandahar city.
The dead included thirteen policemen and six children.
Police and civilians inspect today's blast site in Kandahar province
Kandahar governor Assadullah Khalid blamed the Taliban.
The Taliban, behind a surge of suicide attacks against foreign forces and the Afghan government, could not immediately be contacted for comment.
The Interior Ministry said it was the bloodiest attack since US-led troops overthrew the Taliban government in 2001. It will add urgency to a debate about how the United States and Afghanistan's other allies can help stem militant violence and promote stability.
In November, a suicide bomb attack against a group of lawmakers and subsequent firing by police killed more than 75 people, including six politicians, in the northern province of Baghlan. After that blast, it was not clear how many were killed by the bomb and how many by the police firing.
Dog-fighting is a popular pastime in Afghanistan. The hardline Taliban banned it during their rule, along with other forms of entertainment such as music, dancing and television.
Kandahar is a stronghold of the Taliban who largely rely on suicide attacks and roadside bombings in their campaign to force foreign troops out of Afghanistan and topple its government.
Despite the presence of more than 50,000 foreign troops led by Nato and the US military, as well as some 140,000 Afghan troops, the militants have made a comeback in the past two years, and more than 11,000 people have been killed in violence.