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Story highlights

According to a U.S. defense official, attackers detonated a vehicle at the fence line, with insurgents getting through the fence and using grenades.

Enemy-initiated attacks in Afghanistan are down about 9% from last year for the same time period.

(CNN) —  

A deadly attack on a NATO coalition base in Afghanistan used an improvised explosive device deployed through a vehicle to breach the perimeter of the base, the Pentagon confirmed on Monday.

“The attackers did get on the base through a breach created by a vehicle-borne IED,” Pentagon spokesman Capt. Jeff Davis said, referring to the attack on Camp Integrity in Kabul on Friday.

According to a U.S. defense official, attackers detonated the vehicle at the fence line, with insurgents getting through the fence and using grenades and small arms to shoot at people and buildings. The official said the attack was quickly put down, though a gun battle was audible for half an hour.

One American was killed in the attack, a defense official told CNN. Another official told CNN that nearly 20 people of varying nationalities were wounded.

READ: Taliban leader Mullah Omar’s death could lead to more ISIS recruits

Davis said that while the Pentagon did not know the total number of adversaries, four were killed in the battle. Davis also said that enemy-initiated attacks in Afghanistan were down about 9% from last year for the same time period.

But the fact that insurgents were able to breach the security perimeter of a base is significant. In 2012, insurgents managed to carry out an attack on Camp Bastion, resulting in the deaths of two Marines.

Separately, U.S. Army Col. Brian Triebus said in a statement that eight Afghan civilian contractors were also killed in the incident.

Camp Integrity houses U.S. and coalition troops that help train Afghan forces.

Taliban spokesman Zabiullah Mujahid said the group was responsible for the attack on the NATO base and for a suicide bombing that took place at the National Police Academy earlier in the day.

The attack was part of a deadly day in Afghanistan in which more than 50 people were killed in three separate attacks.