The top U.S. commander in Afghanistan announced Thursday five American soldiers recently were wounded battling Islamic State fighters.

Gen. John Nicholson, who commands U.S. and NATO forces there, said none of the wounds were life-threatening. Three of the soldiers were evacuated from the area and two returned to duty.

Nicholson said the casualties occurred "in the last few days" but did not get into specifics. He said they were hit by small arms fire and shrapnel.

The Americans were partnering in combat with Afghan special forces retaking territory previously controlled by ISIS in the eastern province of Nangarhar, the general added.

Nicolson was speaking to reporters at the Pentagon from his headquarters in Kabul.

On Wednesday, he told The Associated Press the presence of ISIS in Afghanistan was directly linked to its parent organization in Iraq and Syria.

Nicholson said ISIS loyalists in Afghanistan had financial, communications and strategic connections with leadership based in a self-declared caliphate in Iraq and Syria.

"They have applied for membership, they have been accepted, they had to meet certain tests, they have been publicized in Dabiq," the ISIS magazine, he said.

The Afghan offensive, with U.S. support, began on Saturday, hours after ISIS claimed responsibility for a suicide bomb attack in the capital, Kabul, that killed around 80 people.

It was the worst attack in Kabul since the Taliban's insurgency began in 2001. More than 200 people were wounded.

Until recently, Afghan and U.S. officials have insisted that ISIS loyalists were disaffected Taliban weary that their own fight had failed to make headway, after 15 years, in its goal of overthrowing the Kabul government. This week, the spokesman for U.S. forces in Afghanistan, Army Brig. Gen. Charles Cleveland, said that ISIS operatives in Afghanistan numbered between 1,000 and 3,000 loyalists -- though probably closer to 1,500.

Afghan security forces, backed by U.S. air strikes, have been targeting ISIS in Nangarhar holdouts for several months.

The Associated Press contributed to this report.