The Afghan Interior Ministry said in a statement that the blast in Nangrahar province occurred when a passing police vehicle hit a mine. The ministry called it a terrorist act, implying the mine had been planted by insurgents.
Buz Mohammad, the province's deputy public health chief, said four children were killed. He also told The Associated Press that 43 people, most of them children, were wounded.
Ahmad Zia Abdulzai, the spokesman for the provincial governor, told the AP earlier that the wounded included three U.S. soldiers. NATO's International Security Assistance Force said nine of its soldiers were wounded, but could not specify their nationalities.
Abdulzai said the soldiers were visiting a road construction project funded by the United States. He said two children and a policeman were killed. The discrepancy in death tolls could not immediately be reconciled.
In a separate attack in the province, four Afghan policeman were killed when a remote-controlled bomb blew up their vehicle in the Khagyani district, Abdulzai said.
Also Wednesday, at least 13 people were injured in an explosion at a market in Khost province in eastern Afghanistan, said Amir Pacha Mangal, director of the provincial health department. Police were investigating the cause of the blast.
The deaths of civilians, especially children, are an increasingly sensitive issue in the Afghanistan conflict. On Wednesday, the independent human rights watchdog group Afghanistan Rights Monitor said more than 1,050 children under 18 died last year in war-related incidents.
The group said about two-thirds of the young victims died at the hand of insurgents, including several murdered on suspicion of spying. But it also criticized Afghan and international forces, pointing particularly to the alleged deaths of eight children in an operation involving foreign troops last month in Kunar province.
NATO claims those killed in the operation were insurgents, but ARM said in a statement that it appeared to be a "crime against civilian people."
Aside from outright killings of children, the insurgents are endangering countless others by "widespread and systematic attacks on aid workers, humanitarian convoys and facilities (that) deprived thousands of children from lifesaving services such as food aid and immunization against deadly diseases," ARM said.
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Associated Press writers Jim Heintz and Amir Shah in Kabul contributed to this report.
