WASHINGTON, Nov. 25 (Xinhua) -- Commander of U.S. forces in Afghanistan John Campbell said on Wednesday that a deadly U.S. airstrike on an Afghan hospital last month was "caused primarily by human error," admitting that some members of U.S. forces involved in the incident did not follow the rules of engagement.

"The medical facility was misidentified as a target by U.S. personnel who believed they were striking a different building several hundred meters away where there were reports of combatants," said Campbell in a Pentagon briefing from Afghanistan.

"The personnel who requested the strike and those who executed it from the air did not undertake appropriate measures to verify that the facility was a legitimate military target," added Campbell, calling the incident "tragic but avoidable".

A U.S. AC-130 gunship on Oct. 3 devastated an Afghan hospital run by Doctors Without Borders, an international medical aid agency also known by its French language acronym MSF, killing at least 30 civilians and injuring another 37.

According to Campbell, MSF on Sept. 29 sent the coordinates of its Afghan facility in Kunduz to multiple recipients within the U.S. and NATO chains of command, and MSF contacted U.S. military personnel 12 minutes after the strike began.

However, it took another 17 minutes for U.S. headquarters and the U.S. special operations commander to realize the fatal mistake, said Campbell, adding that the whole strike lasted for about 29 minutes.

During the airstrike, 211 shells were fired by the U.S. warplane at the hospital compound.

In addition to human errors, which included problems with the planning and approval process employed during the strike and the lack of a single system to vet proposed targets against a no-strike list, Campbell also cited malfunction of the electronic communication system onboard the warplane as a factor in the incident.