Afghan aid workers and civilians will suffer the most after the deadly U.S. bombing of a hospital run by the charity Medecins Sans Frontieres (MSF) in the northern city of Kunduz, experts said on Friday.

At least 22 patients and MSF staff were killed on Saturday when a U.S. aircraft attacked the hospital during fighting between Afghan government troops and Taliban forces.

MSF, which wants an independent international probe into the airstrike, says it has withdrawn its staff from Kunduz and is reviewing all its operations in Afghanistan “to carefully weigh the safety and security of staff and patients.”

“MSF's decision to withdraw (from Kunduz), which is unfortunate but completely understandable, could have catastrophic consequences for civilians in the broader region,” said Michael Kugelman, senior programme associate for South Asia at the Woodrow Wilson Center.

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“There are medical facilities in Kunduz and throughout northeastern Afghanistan, but the MSF hospital was the only one that could handle major war injuries. And yet at least for now it has closed down.”

Kugelman said he feared that with the Taliban emboldened by its brief seizure of Kunduz, it will step up its offensives in surrounding districts and result in more civilian casualties.

Local Afghan charities will need to take on an even greater burden than they already bear, with the very real threat of diminished international humanitarian assistance, he added.

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MSF, which has been in Afghanistan since 1980, pulled out for a period after five staff were killed in 2004. It has already shut down its hospital's operations in Kunduz and has given no indication of when it might reopen.

The Aid Worker Security Database, a project set up by the research consultancy Humanitarian Outcomes, says 65 aid workers have been killed in attacks in Afghanistan so far this year, compared to 127 the previous year.

Humanitarian Outcomes' Adele Harmer said recruitment has long been one of the most difficult challenges for humanitarian agencies, and in dangerous or hardship posts like Afghanistan, the challenge of attracting experienced staff is still greater.

“For the most part however, it is important to recognise that it is national and local staff who are doing the majority of the field work in Afghanistan, not internationals,” said Harmer.

“Local staff are often motivated by a desire to help within their own communities, and don't always see the risks as the same, nor do they necessarily see these contexts as 'hardship' posts.”