WASHINGTON — President Obama personally apologized on Wednesday to the head of Doctors Without Borders for what he described as the mistaken bombing of its field hospital in Kunduz, Afghanistan, promising a full investigation into the episode, which took the lives of nearly two dozen doctors and patients.

But five days after an American AC-130 gunship devastated the medical facility, Mr. Obama's personal expression of regret in a telephone call from the Oval Office appeared to do little to satisfy the leader of the doctors group, who issued a terse statement saying the president's apology had been "received."

Dr. Joanne Liu, the international president of Doctors Without Borders, repeated her demand for an independent investigation led by the International Humanitarian Fact-Finding Commission to "establish what happened in Kunduz, how it happened, and why it happened."