NATO's top commander in Afghanistan has ordered tens of thousands of troops to be retrained in the coming days in how to avoid civilian casualties during counter-insurgency operations.

U.S. General John Allen announced the retraining program in a letter to Afghan President Hamid Karzai, who has frequently complained about deaths and injuries to Afghan civilians caught in the crossfire of NATO operations against Taliban militants. A U.S. military official confirmed the letter and its contents in an email sent to VOA on Tuesday.

In the letter, General Allen says NATO forces will aggressively pursue retraining in methods of employing force against insurgents while protecting Afghan civilians. He ordered all NATO units to complete the retraining by Monday. NATO has about 140,000 troops in Afghanistan fighting a 10-year-long Taliban insurgency, with around 100,000 of those from the United States.

Meanwhile, Afghan officials say a NATO mortar attack on Sunday killed three women and injured at least one child in the Zhari district of Afghanistan's southern province of Kandahar. Last week, an airstrike targeting insurgents killed six children and one adult in the same area.

NATO troop commanders say Taliban and other insurgents regularly use Afghan civilians as human shields while attacking coalition and Afghan security forces and officials.