KANDAHAR, Afghanistan (AP) — A tribal elder was gunned down Tuesday while he was shopping in Kandahar, the latest targeted killing ahead of a NATO-led operation here that will be a critical test of the Afghan war.

The Taliban claimed responsibility for the attack, saying Hayat Khan was "dealing with Americans and working against us." Khan was a member of a district shura, a traditional meeting of elders and community leaders called upon to solve local issues, said Zulmai Ayubi, a spokesman for the Kandahar provincial governor.

The attack highlights the challenges facing NATO forces ahead of a U.S.-led operation planned for this summer that aims to clear Kandahar of Taliban fighters. Kandahar is the largest city in the south and the birthplace of the Taliban, which still has considerable support here.

NATO reported two of its service members died in southern Afghanistan on Monday, one in a roadside bombing, the other in a vehicle accident, bringing the number of international soldiers killed so far this month to six.

Also Tuesday, more than 20 students at a girls' school in the capital Kabul were briefly hospitalized after what officials said was a suspected poison gas attack by militants who oppose education for girls.

"This is the work of those who don't want Afghan people to get an education and find their way toward development, progress and a life of happiness," President Hamid Karzai said in a statement.

There have been similar cases of mass illness in the past, including last month in the northern province of Kunduz. Some believe the illnesses could be cases of mass hysteria in areas threatened by the Taliban and their militant allies. They also could be the result of accidental poisonings, such as from fertilizers.

In the south, the Taliban have launched increasingly deadly attacks ahead of the planned NATO operation in Kandahar. Since April 12, at least 20 civilians have been killed in Kandahar, including children. Aid workers also have been targeted.

Last month, gunmen stormed a mosque and killed the deputy mayor of Kandahar as he knelt for evening prayers.

The looming offensive and the ongoing crime and insecurity have rattled the city's half million inhabitants, who are deeply skeptical of Western promises.

President Barack Obama has ordered 30,000 more troops into Afghanistan, in part to back up the Kandahar offensive.

Also Tuesday, a former member of southern Zabul province's women's affairs department was fatally shot, said Mohammad Jan Rasoulyar, a spokesman for the provincial governor. Police were investigating.

In Kunduz on Tuesday, Taliban militants killed two civilians they accused of spying for the government, said Muhbobullah Sayedi, a spokesman for the provincial governor.

On Monday, a joint operation between Afghan and NATO forces killed five militants in central Afghanistan, the defense ministry said. Several militants also were arrested in Monday's operation in Gezeb district of Daykundi province. All were involved in "disrupting security" in the area and planting roadside bombs, the ministry said.