By ALISSA J. RUBIN
KABUL, Afghanistan — Two gunmen on a motorcycle shot and killed a policewoman in western Afghanistan on Thursday, wounding her daughter and two other family members who were with her. It was the fourth killing of an Afghan policewoman in the last six months.
“Her name was Masooma, and she was very active in her job,” said Gen. Abdul Rahim Chikhansori, the acting police chief for Nimruz Province. “The enemy of Afghanistan didn’t tolerate her great service and active approach, and unfortunately she was martyred.”

There were conflicting reports about which relatives were with her and the extent of the injuries to her daughter and the two others, who may have been her children or her daughter’s children.

The attack took place on the outskirts of Zaranj, the provincial capital, early Thursday morning, as Ms. Masooma, who like many Afghans used only one name, was taking her young relatives to school before going to work.

Female police officers, especially in more rural areas, are extremely vulnerable. That is partly because there are so few of them that they are easily spotted, and also because of an ingrained cultural resistance to women taking public roles.

“For a woman, being a member of the police force is not acceptable to many in Afghan society,” said Georgette Gagnon, the head of human rights for the United Nations in Afghanistan.

There are just 37 policewomen in all of Nimruz Province, said Farida Hamidi, a member of the Parliament from the province, who was nearby at the time of the shooting.

Ms. Masooma worked as a searcher and was often stationed at the governor’s compound to frisk women as they entered the building, said Ms. Hamidi, who said she recalled frequently seeing the policewoman at her post.

Like many women in the police force, Ms. Masooma took the job out of necessity.

“She was 48 years old, and she was a widow. She had children and was the breadwinner for the family,” Ms. Hamidi said. “She used to come to me whenever she had problems as a woman and police officer because I used to serve as director of women’s affairs before going to the Parliament.”

The police have not caught the gunmen, and no one has claimed responsibility for the killing.

Two of the three other policewomen killed this year were in Helmand, a predominantly Pashtun province that borders Nimruz. The third was in Nangarhar, also a predominantly Pashtun province, but in the far east of Afghanistan.

In much of Afghanistan, the idea of a woman working outside the home is only beginning to be accepted, but employment as a policewoman is still viewed as shameful by many people because it often means working side by side with men.

Nimruz, a province in the far west of the country that borders Iran and Pakistan, has become increasingly unstable, according to local officials.

And the audacity of the crime, taking place in broad daylight on a public road, is a signal of the increasing lawlessness in the area, said Mohammad Nader Baloch, the deputy chairman of the provincial council.

“This is not the first incident in which the terrorists are conducting an assassination attempt in daylight in the middle of the city,” Mr. Baloch said. “But the authorities have failed to control them.”

Jawad Sukhanyar and Taimoor Shah contributed reporting.