Earlier on Friday, five children died in southern Helmand province when an unexploded shell they had found went off.
According to Taliban-appointed Herat provincial spokesman Mahmood Rasoly, the two bombs went off among civilians at a field used for traditional Afghan games such as mud wrestling and Buzkashi, played with horse-mounted players.
No one immediately claimed responsibility for the bombing in Herat.
Another Taliban official in the province, Naeemulhaq Haqqni who is chief of the Herat Information and Culture Department, said the Taliban found and defused two other bombs also planted in the same playing field.
In the explosion in Helmand, the children, aged between three and 12 years, appeared to have discovered the shell and were playing with it in the district of Marja, when it suddenly went off, said Abdul Bari Rashid Helmandi, a Taliban media officer in the province.
A former local council member, Ahmadullah, who like many Afghans goes by only one name, said two other children were injured in the explosion and were being treated in the district hospital.
Afghanistan remains highly dangerous for children, who often collect scrap metal to sell to support their families.
Many are killed or maimed when they come across unexploded ordinance.
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