A suicide attack in eastern Afghanistan killed 25 people Tuesday, the police chief in Nangarhar province said.
Chief Abdullah Stanikzai said the attack happened during the funeral of a local elder in the Dor Baba district, near the border with Pakistan.
Fifty people were injured in the incident, local officials reported. Among the wounded was the district chief of Dor Baba, Stanikzai said.
Afghan President Hamid Karzai condemned the attack, in a statement from his office.
While it is not yet clear who was behind the blast, it is the latest of many to strike Afghan civilians.
A recent United Nations report found that while violence against the Afghan population fell in the first half of the year, it is still taking a "devastating toll on civilians."
About 80% of the attacks against civilians are by anti-government forces such as the Taliban, the report said.
Nangarhar, which has Jalalabad as its capital and borders Pakistan's restive Khyber Pakhtunkhwa province, has seen several recent International Security Assistance Force operations targeting militants.
Afghan and coalition security forces arrested an alleged Taliban bomb-making expert in Nangarhar's Khugyani district earlier Tuesday, an ISAF statement said.
The man "is believed to be a leading figure in the movement and provision of explosives for attacks against coalition and Afghan security forces throughout eastern Nangarhar," the statement said.
Several other suspected insurgents were seized in the same operation, as well as firearms, military uniforms and explosives, it said.
A separate operation last week in Nangarhar's Hisarak district led to the arrest of an alleged Taliban insurgent accused of using his status as a member of the Afghan National Police to conduct an attack in May which killed two coalition service members in Helmand province, ISAF said.
Prior to his capture, the man was attempting to join the Afghan National Army, ISAF said.
U.S. forces take a leading role in ISAF operations in Nangarhar.