KABUL (Reuters) - A U.S. soldier has been taken into custody after an Afghan detainee was found dead in his cell in southern Afghanistan at the weekend, apparently from a gunshot wound, the U.S. military said on Tuesday.

Afghan President Hamid Karzai’s office issued a statement saying Karzai had ordered an investigation into the death.

The U.S. military said it had opened a criminal investigation. “The detainee, who died of an apparent gunshot wound, was being held temporarily at an Afghan government facility under U.S. guard,” it said in a statement.

He was “known to be a senior leader of the Taliban network in Arghandab,” a district north of the provincial capital of Kandahar.

The NATO-led International Security Assistance Force (ISAF) initially said a man captured during an operation in Kandahar on Saturday had been found dead in his cell the next day.

Karzai’s palace said coalition forces had entered the prison in Kandahar, the birthplace of the Taliban, on Sunday night and killed the detainee, who it named as Mullah Mohebullah. It used a word that can be translated as “killed” or “murdered.”

Violence is at its worst across Afghanistan since the Taliban were ousted by U.S.-backed Afghan forces in late 2001, with military and civilian casualties at record levels despite the presence of almost 150,000 foreign troops.

FRICTION

Foreign troops have made progress in offensives launched in the south over the past 16 months in an attempt to turn the tide against the Taliban-led insurgency. Thousands of mainly U.S. troops began a new offensive this month around Kandahar city.

Civilian casualties and the deaths of detainees in the custody of foreign troops are a major source of friction between Karzai’s government and Washington, where a review of the Afghan war strategy will be conducted in December.

On Saturday, a report by U.S.-based think tank Open Society Foundations said former detainees held at a secret U.S. prison at Bagram, separate to the main Bagram jail near Kabul, had reported abuse at the hands of the U.S. military.

In the report, former detainees said jailers mistreated them by depriving them of natural light, failing to provide proper food and withholding Red Cross visits.

A spokeswoman for U.S. military detention operations said the International Committee of the Red Cross was aware of the temporary holding centers it operates and that all treatment complied with international and U.S. laws.

The old Bagram jail was replaced this year by a $60 million prison which Washington says meets international standards.

Apart from Bagram, there are smaller jails on foreign military bases around Afghanistan where detainees are held before they are taken to Bagram or handed over to Afghan authorities.

Earlier this year, there were around 1,000 prisoners held in foreign military detention centers in Afghanistan, more than 800 of them in the main jail at Bagram.