In the south, an Afghan soldier opened fire on NATO troops at the Kandahar airport, killing one service member, the alliance said.
In the attack in the western province of Herat, Taliban militants fleeing a joint Afghan police and army patrol placed a roadside bomb along a village road in an attempt to kill the government troops, local police Lt. Sher Agha said.
But the bomb went off instead next to a cart that was carrying 12 women, four children and one man, killing all of them, Agha said.
NATO gave no details on the blast at the Kandahar airport, an important base in southern Afghanistan that is guarded by Slovakian troops.
Kandahar Air Field commander Gen. Abdul Raziq Sherzai initially said three Slovakian troops were wounded in the shooting. It was not immediately clear whether one of the wounded soldiers had died or whether the fatality was a fourth victim.
There has been a string of insider attacks recently, in which Afghan forces open fire on their comrades or international forces. The attacks threaten to shake the confidence of the two sides as the 2014 target date approaches for the withdrawal of most of the international troops from Afghanistan.
The attacker was taken into custody after the morning incident and was questioned, said Kandahar government spokesman, Javid Faisal.
Faisal said a preliminary investigation indicated the shooting was an accident rather than a so-called insider attack.
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