Suspicion has fallen on sympathizers of the Taliban, the hard-line Islamist militia that opposes education for women and prohibited girls from going to school when it was in power until it being ousted by a 2001 U.S.-led invasion.

Poisonous levels of organophosphates were found in samples taken from girls sickened in incidents over the past two years, said ministry spokesman Dr. Ghulam Sakhi Kargar.

Samples from more recent cases have been sent to Turkey for analysis and no results have been issued yet, Kargar said.

Last month, 48 pupils and teachers at Kabul's Zabihullah Esmati High School and 60 students and teachers at the Totia Girls School were hospitalized after fainting or complaining of breathing problems, dizziness and nausea.

Students say they began feeling unwell after being exposed to an unknown gas spreading through classrooms.

Most were released within hours. It remains unclear how the gas spread.

In addition to killing weeds and insects, organophosphates are the active ingredients of deadly nerve gases such as sarin and VX, and even low-level exposure can damage the nervous system.

Signs of organophosphate poisoning include headache, tiredness, upset stomach and breathing trouble, all similar to the symptoms shown by the students and teachers at the Kabul schools.

Meanwhile, a Muslim religious leader was killed by a bomb attack and a US service member died in fighting Wednesday in turbulent southern Afghanistan, officials said.

Aid group Oxfam, meanwhile, said it was suspending operations in the northeastern province of Badakhshan following the deaths of two employees and a local volunteer in a roadside bomb attack.

Also Wednesday, Afghanistan's central bank tried to shore up confidence in Kabul Bank, the country's biggest financial institution, after its top executives resigned amid allegations of mismanagement and corruption.

The Muslim leader, Mohammad Hassan Taimuri, was killed in Kandahar city by a remote-detonated bomb hidden on a motorcycle that exploded in a downtown square, Kandahar police chief Sher Mohammed Zazai said. One other person was killed in the attack and two people were wounded, Zazai said.

There was no immediate claim of responsibility, and it was not clear why anyone would target Taimuri, who was responsible for managing Islamic religious institutions.

However, Taleban insurgents who are highly active in Kandahar routinely target government figures and institutions, often indiscriminately. The city is a longtime stronghold of the hard-line movement and the focus of the American-led operation against the insurgents.

NATO gave no other information about the U.S. serviceman's death, the first of the new month and the 20th in less than five days. The U.S. death toll for August stood at 56 _ three-quarters of them in the second half of the month as the Taliban fought back against U.S. pressure.

Oxfam also gave no details about the three Afghans killed, but said it was reviewing security arrangements and had no plans to suspend its overall operations in Afghanistan, which range from running schools to distributing livestock.

Badakhshan's deputy governor, Shamsul Rahman, said the three were killed Saturday when their vehicle was struck by a roadside bomb suspected to have been set by Taliban insurgents.

Formerly relatively peaceful, Badakhshan has seen rising insurgent violence, and in early August, a group of suspected insurgents in the province murdered 10 aid workers — six Americans, two Afghans, one German and a Briton — who had spent two weeks giving vision and other medical care to impoverished villagers in neighboring Nuristan province.

In another development, Bosnia's Parliament on Wednesday endorsed a decision by the country's presidency to send a 45-man strong infantry unit to join the NATO-led mission in Afghanistan.

The Bosnian Army unit will be deployed in October in Helmand province in southern of Afghanistan and will guard the Danish contingent's military base.