The Pentagon is to make "condolence payments" to families of victims of a US air strike that mistakenly hit a Doctors Without Borders hospital in Kunduz, Afghanistan, killing 22 people.

"The Department of Defense believes it is important to address the consequences of the tragic incident at the Doctors Without Borders hospital in Kunduz, Afghanistan," spokesman Peter Cook said in a statement on Saturday, adding the US would also pay to repair the charity hospital.

"US Forces-Afghanistan has the authority to make condolence payments and payments towards repair of the hospital," Cook said.

"USFOR-A will work with those affected to determine appropriate payments. If necessary and appropriate, the administration will seek additional authority from the Congress."

US President Barack Obama on Wednesday apologised to Doctors Without Borders for the bombing of its hospital.

The medical charity, which lost 12 of its staff and 10 patients, is pressing for an international commission to investigate what it calls a war crime.

Afghan investigation

Earlier on Saturday, Afghan President Ashraf Ghani appointed a team of investigators to look into the air strike as well as the circumstances that led to the Taliban's brief capture of Kunduz.

The five-man delegation, appointed by presidential decree, will leave soon for the northern city to conduct a province-wide probe into how the Taliban were able to overrun the city on September 28 and hold it for three days, before government troops launched a counter offensive, Ghani's office said.

The team will be led by the former head of the national intelligence agency, Amrullah Saleh, and will report to the president.

Representatives of Doctors Without Borders met with Ghani and his national security adviser Mohammad Hanif Atmar on Friday, his office said in a statement.

Ghani told them he had ordered Afghan security forces to ensure the protection of humanitarian organisations.

The statement quoted him as saying investigations were needed "so that we know what happened in the incident, how information was collected, and how the incident happened based on that information".

'Loss of innocent life'

Doctors Without Borders has called for an independent probe of the incident by the Swiss-based International Humanitarian Fact-Finding Commission.

The commission is made up of diplomats, legal experts, doctors and some former military officials from nine European countries, including Britain and Russia.

It was created after the Gulf War in 1991, and has never deployed a fact-finding mission.

The air strike was requested by Afghan ground forces, according to the commander of US forces in Afghanistan, General John F Campbell, but mistakenly hit the hospital.

On Tuesday, Defense Secretary Ash Carter said the US military deeply regretted the loss of life and was acknowledging its mistake and working to understand what went wrong.

"The US military takes the greatest care in our operations to prevent the loss of innocent life, and when we make mistakes, we own up to them. That's exactly what we're doing right now," Carter said in a statement.

Source: Agencies