Karzai condemns NATO airstrike; Panetta arrives in Kabul

Kabul, Afghanistan (CNN) -- Afghan President Hamid Karzai condemned a NATO airstrike this week that a provincial official says killed women and children, in a statement that came just as U.S. Defense Secretary Leon Panetta arrived Thursday in Kabul for talks.

A provincial official has said among the dead in the airstrike were civilians, while the NATO-led International Security Assistance Force said initial reports revealed only two injuries.

ISAF is aware of the claims of civilian casualties and was looking into what took place, a spokesman for the coalition said.

The NATO airstrike Tuesday in eastern Afghanistan's Logar province, along the volatile Pakistan border, is likely to strain already tense relations with the United States.

In the statement, Karzai said he was cutting short a trip to China where he has been attending a summit.

"NATO operations that inflict human and material losses to civilians can in no way be justifiable, acceptable and tolerable," Karzai said.

The allegations of civilian casualties came as Panetta was set to begin discussions with U.S. Army Gen. John Allen, commander of ISAF troops, and Afghan Defense Minister Gen. Abdul Rahim Wardak.

High on the list of discussion topics is likely to be the training of Afghan security forces.

With American troops due to withdraw from Afghanistan by the end of 2013 under a timetable announced by President Barack Obama, the U.S. military is beefing up its training of Afghan forces.

The latest allegations of civilian casualties also come at a critical time for the United States.

While publicly U.S. military and political officials have said Afghanistan will be ready to take over security of its country by the time NATO troops depart, critics have said there are questions about whether Afghan forces can stand on their own.

Violence has increased in recent weeks, coinciding with the start of the Taliban's summer fighting season.

This marks Panetta's fourth visit to Afghanistan.

It was not immediately clear if Panetta would be meeting with Karzai upon his return.

The last meeting between the two in March came on the heels of allegations that a U.S. soldier snuck off his base in southern Kandahar province and went on a shooting spree in two villages that left 17 people dead.

At the time, Karzai called the shootings a cruel act against the people of Afghanistan, and told Panetta that Afghans have lost trust in international forces.

The shooting spree followed revelations that U.S. troops inadvertently burned copies of the Quran and other Islamic religious materials, which sparked massive, violent protests.

Military officials said the materials had been seized from Afghan prisoners because they contained extremist messages.