Four Afghan police officers died in a NATO air bombardment in the eastern province of Nangarhar, an official with the International Security Assistance Force told Efe on Thursday.

The incident took place Wednesday night along the highway linking the Afghan city of Jalalabad with the Torkham border crossing point into Pakistan.

"The Afghan forces requested air assistance. An ISAF aircraft responded ... and as a result of the bombardment four Afghan police officers lost their lives. We very much regret what happened," said an ISAF spokesman by telephone.

She added that the ISAF had launched an investigation into the incident.

Afghan security forces had requested help because a checkpoint was under attack by insurgents, according to a communique issued by the Nangarhar governor's office.

In addition, two Afghan police officers were wounded and an undetermined number of insurgents were killed.

Incidents where members of the Afghan security forces have died in operations by foreign troops are much less frequent than incidents where civilians have died.

The latter cause great friction between the Afghan government and the foreign troops deployed around the country.

Afghan President Hamid Karzai, in fact, has requested on numerous occasions that allied air strikes be limited or halted altogether.

ISAF counterinsurgency activities in Afghanistan have been falling off gradually since in 2011 international forces began their phased withdrawal from the country and the transfer of control over security to the Afghan army and police. EFE