KABUL, Afghanistan — The French military took responsibility on Friday for killing four Afghan children during a missile strike in early April, and NATO said it was investigating allegations of a military convoy gunning down two Afghan women and a girl in southeastern Afghanistan.

The reports underscore concern over rising civilian deaths caused by the American-led military coalition as troops step up operations across the country. Last June, the new NATO and American commander, Gen. Stanley A. McChrystal, instituted guidelines credited with reducing civilian casualties caused by Western military forces.

That downward trend has abruptly been reversed: In the first three months of 2010, at least 72 Afghan civilians were accidentally killed by troops, compared to about 30 killed in the same period last year, according to a NATO official in Kabul.

The latest allegations of civilian deaths were in some dispute. On Friday, Afghan officials said international forces killed two Afghan women and a girl riding in a car in Zabul Province as they approached a military convoy stopped on the road to remove a buried bomb.

A spokesman for the Interior Ministry in Kabul, Zemary Bashary, said “foreign forces” had killed the women in Zabul.

Mohammed Jan Rasool Yar, a spokesman for the Zabul governor, said the Afghan authorities had not determined which military unit shot the women. He said the driver of the car, a man, was wounded and hospitalized.

As troops defused the bomb, Mr. Yar said, a Toyota approached. They “tried to stop them, but they did not stop,” he said, and troops opened fire.

But while a NATO spokesman in Kabul said early Saturday morning that one military convoy had fired warning shots at a civilian car, he said that the driver stopped and there were no casualties. The spokesman said that NATO forces were continuing to investigate the allegations of civilian casualties in Zabul, but that they had no confirmation of any involvement by NATO troops.

Also on Friday, the French military said its own investigation found that its forces killed four children during a fight with insurgents on April 6 in Kapisa Province, north of Kabul.

According to Rear Adm. Christophe Prazuck, a French military spokesman, French and Afghan forces were setting up a combat outpost when insurgents attacked in the Bedrau Valley. Forces at a checkpoint returned fire and drove them back, he said.

As the militants regrouped, French observers spotted seven insurgents hidden behind a wall, and troops fired one antitank missile.

Thirty minutes later, a civilian vehicle arrived at the checkpoint with four children, ages 10 to 15, said to have been wounded in the attack, and another child who had already died. Three of the wounded children died shortly thereafter.

“The children were near the insurgents and beneath a tree,” Admiral Prazuck said. “No civilian activity had been observed.”

A French military investigation concluded in recent days. No further investigation or punitive measures are planned, Admiral Prazuck said.

Late Wednesday night, a relative of an Afghan member of Parliament was shot and killed during an operation involving NATO forces in Nangarhar Province, setting off angry demonstrations the following morning that blocked the main road to Kabul for an hour amid chants of “Death to America.”

The lawmaker, Safia Sidiqi, said troops came to her house just before midnight. She was in Kabul at the time, but she said her brother had called her to say there were thieves outside the house. She said she had called the provincial police and was told that American troops were conducting an operation.

“They came to my house intentionally and killed one of my family members,” she said. “The Americans knew this was my house.”

NATO officials said troops from a joint NATO-Afghan force had killed “one armed individual” while pursuing a “Taliban facilitator.” In a statement, NATO said the man had been shot and killed after aiming his weapon at the troops and ignoring commands and hand signals to lower his gun.

Richard A. Oppel Jr. reported from Kabul, and Scott Sayare from Paris. Sharifullah Sahak contributed reporting from Kabul.