An Afghan official said police are investigating a rocket strike in southern Helmand province that killed at least 26 people at a wedding, many of them women and children.
At least 50 other people were wounded in the attack Wednesday.
Police say the rocket appears to have been fired from a nearby army checkpoint.
General Mahmoud, the deputy Commander of the Afghan 215 corps in the province, said artillery was fired from three directions at a village in Sangin district where the wedding was held on Wednesday.
“What we know so far is that our soldiers fired mortar rounds from three outposts but we do not know whether it was intentional,” Mahmoud told Reuters. “We have launched our investigation and will punish those who did this.”
Thursday is the day Afghanistan officially takes full responsibility for its own security with the end of the United States and NATO combat mission.
About 12,000 U.S. and NATO personnel will remain to train, advise and assist Afghan police and the army.
The move will test the readiness of 350,000 Afghan forces who will bear responsibility for fighting increasingly organized Taliban insurgents.
“I want to congratulate my people today that Afghan forces are now able to take full security responsibility in protecting their country's soil and sovereignty,” President Ashraf Ghani said in a speech to mark the handover.
The Taliban is claiming victory in the 13 year-long war with Western and Afghan troops.
Nearly 3,500 foreign troops were killed. More than 2,200 of them were Americans.
The U.S. invaded Afghanistan to overthrow the Taliban regime, which was sheltering the al-Qaida masterminds of the September 11, 2001 terrorist attacks.
At least 3,188 Afghan civilians were killed in the intensifying war with Taliban insurgents in 2014, making it the deadliest year on record for non-combatants, the United Nations said in a report last week.
As of Nov. 30, the United Nations had recorded a total of 3,188 civilian deaths and 6,429 injuries.
The numbers are a sharp reminder that the Afghan war is far from over.
For the first time, ground battles between the Taliban and Afghan forces became the main cause of civilian deaths in 2014. In previous years, planted bombs killed the most civilians.
While U.S. military officials have portrayed the war as in the process of being won by Afghan security forces, the national army and police have also suffered record losses this year, with more than 4,600 killed.
Some material for this report came from Reuters.