A top U.S. military commander says American forces are responsible for "mistakenly" hitting a hospital in Kunduz, Afghanistan, in an aerial bombardment Saturday that killed 22 people.

Army General John Campbell told a congressional committee in Washington that Afghan forces requested the airstrike on the hospital operated by the international medical charity Doctors Without Borders because Taliban insurgents were firing from the facility.

But he said the U.S. conducted the half-hour-long raid after reviewing the request.

"To be clear, the decision to provide aerial fire was a U.S. decision made within the U.S. chain of command," Campbell said.  "A hospital was mistakenly struck.  We would never intentionally target a protected medical facility."

The hospital in Kunduz after an alleged U.S. airst
The hospital in Kunduz after an alleged U.S. airstrike Saturday killed at least 19 people, including three children, according to officials with the international medical charity Doctors Without Borders, known by its French acronym MSF.

Campbell, who heads the NATO-led coalition in Afghanistan, declined to discuss further specifics about the airstrike as U.S. and Afghan investigations continue.

At the White House, spokesman Josh Earnest called the bombing a "profound tragedy and something the United States takes very seriously."

Doctors Without Borders, known by its French acronym MSF, has condemned the attack that killed 12 of its staff and 10 patients as a “grave” violation of international humanitarian law.

MSF President Joanne Liu said Tuesday that the incident "cannot be brushed aside as a mere mistake or an inevitable consequence of war."

She said the collaboration of the Afghan and U.S. forces implies they "decided to raze to the ground a fully functioning hospital, which amounts to an admission of a war crime.”  MSF has called for an independent probe of the attack.

Taliban, Afghanistan forces clash

Meanwhile, fresh fighting broke out Tuesday in Kunduz, belying days of government claims its forces have evicted and recaptured the beleaguered city from the Taliban.

Afghan security forces and insurgents clashed in the provincial capital’s central square.

?Authorities warned that food and other aid cannot get through to the city in northern Afghanistan. The United Nations says all international aid groups had left Kunduz.

A Taliban spokesman, Zabihullah Mujahid, says its fighters staged an assault on Afghan forces in the early morning and fighting was continuing in several parts of the city.

Insurgents had briefly overrun Kunduz a week ago in a surprise offensive, but Afghan forces wrested back the control three days later and since claimed to have flushed out Taliban militants.

But hostilities have since raged in parts of Kunduz. Insurgents have also captured several districts in two nearby northern provinces, and Afghan forces are battling to regain control of the lost territory.

MSF and the United Nations human rights chief have said the hospital attack could amount to a war crime.

The U.N. said Monday that it would wait for the outcomes of ongoing investigations before deciding whether to support an independent probe.

Residents and aid workers say that recent heavy fighting in Kunduz has caused massive destruction to the infrastructure and conditions in the city are not fit for living.

Afghan officials say the hostilities have prompted thousands of families to flee for safer cities.

Meanwhile, the Taliban claimed responsibility for the overnight attack in Kabul on a building it claimed belonged to the Afghan intelligence agency.  Authorities in the capital announced Tuesday that security forces had killed all three suicide bombers to end a 10-hour siege.

They said seven police officers were also injured during the operation, but gave no further details.