KABUL, Afghanistan - Gunmen stormed a wedding party in eastern Afghanistan, killing nine people including the groom as they opened fire on a crowd of about 30 family members, officials said Thursday.

The assailants entered a field where the groom and his family members had gathered late Wednesday night in the remote Dur Baba district and started shooting, said Ahmad Zia Abdulzai, the provincial government spokesman. The attackers also set fire to a nearby house and a car.

No one immediately claimed responsibility for the attack.

Abdulzai said the cousin of the groom is the chief administrator for Dur Baba district, suggesting that it may have been an insurgent strike against the family for being allied with the government. He said that officials are investigating.

The district administrator, Hamisha Gul, said the insurgents briefly held one of the attendees, saying he was an American spy. Gul said he was not at the gathering but had spoken to family members.

Among the dead were the groom, his father and one of his brothers, Gul said. He said about 20 men had gathered to celebrate and organize the wedding ceremony, which was scheduled for Thursday.

Civilian casualties have spiked because of an increase in insurgent attack in recent years. In 2010, at least 2,777 civilians were killed in Afghanistan, a 15 percent increase over the previous year, according to the United Nations. The increase was attributed entirely to insurgent attacks.

The Taliban and other allied groups have regularly targeted both government officials and those seen as in league with the Afghan administration or international forces. The insurgents have said they do not consider these people civilians.