KABUL, Afghanistan, Aug.9 — Taliban militants killed a widow and her 13-year-old son, accusing them of spying for the government and foreign troops in Helmand province, the Afghan government said today. The woman was shot dead and her son was hanged by an electric wire from a tree Monday, the provincial governor’s spokesman said. In a separate attack late Tuesday night, a group of insurgents attacked an American military base in the north-east of the country with rockets and small arms fire, forcing American troops to fight back with mortars and gunfire. A United States military statement said 13 insurgents were killed in the firefight. The firebase was recently established as part of an expansion of control by American troops into the mountainous region along the Pakistani border.

The killings of the woman and her son occurred in the village of Dast Mastan, near Musa Qala in northern Helmand province, where British troops have been battling insurgents repeatedly in recent weeks. Local officials, including the police chief, informed the provincial authorities about the incident, the spokesman for Helmand’s governor, Haji Mohaiuddin, said.

“They were very poor people and they were accused of spying for the government and the foreign troops,” he said. “Definitely it was done by the Taliban,” he added. Reported denials by a Taliban spokesman were not credible, Mr. Mohaiuddin said: “They deny anything they do, and claim responsibility for things they didn’t do.” Elders and leaders of Helmand province had gathered today in the provincial capital, Lashkar Gah, to condemn the killings, he said. “We all condemned this. This is not an action of a human, or according to Islam,” he said.

United States and NATO military officials said Taliban insurgents are resorting to fear tactics to establish control among the population in parts of Afghanistan. Col. Tom Collins, spokesman for the American-led coalition, said their forces had encountered cases where Taliban insurgents were knocking on doors in one district of Ghazni province, south of Kabul, and demanding that villagers provide one son per family to join the insurgents to fight. NATO spokesmen said they had found similar cases in southern Afghanistan, where their forces are now operating, including a case of Taliban insurgents killing a son after the family refused to give them one of their sons.

President Hamid Karzai, who is fending off an insurgency that has expanded in recent months across the six southern provinces and some eastern provinces, also denounced the killings as against the historical and cultural values of Muslims.

“The gruesome act is unforgivable and no one can justify it. This shameful act is an affront to all Afghans and their historical traditions,” he said in a statement released by his press office.