An explosion outside an entry control point at Bagram Airfield in Afghanistan Wednesday wounded six coalition service members and killed an Afghan linguist, U.S. Forces Afghanistan said. 

Three of the wounded coalition members were American, said Capt. Bill Salvin, a spokesman for U.S. Forces Afghanistan. Three others were from coalition member countries, Salvin said. All six had “non-life threatening injuries” and were able to be treated at the medical facilites at Bagram. 

Salvin said the attack was conducted by a suicide bomber wearing a vest who either approached the troops on foot or on a motorcycle. 

The Wednesday attack came a day after U.S. Forces-Afghanistan formally apologized for an offensive leaflet that was dropped in Parwan, the same province as Bagram Airfield.

Salvin said it was too early to tell whether the leaflet spurred the attack. 

The leaflet, dropped early Tuesday local time in Parwan, was meant to ask local Afghans to report the Taliban to Afghan security forces, said Pentagon spokesman Lt. Col. Mike Andrews.  

“Unfortunately, there was an image on the leaflet that was offensive to Muslims,” Andrews said. 

On Tuesday, the Parwan province governor held a shura with local leaders, where they demanded the apology, Andrews said.

“There is no excuse for this mistake,” Maj. Gen. James Linder said in the apology. ”I am reviewing our procedures to determine the cause of this incident and to hold the responsible party accountable. Furthermore, I will make appropriate changes so this never happens again.

“Resolute Support remains committed to Afghanistan’s future, and I offer my sincerest apologies for this error.”