The NATO occupation continues to face a relentless wave of attacks from within the Afghan ranks. On Sunday, four U.S. soldiers were killed and two others were wounded in a shooting by members of the Afghan police. NATO spokesperson Günter Katz said the killings followed a separate attack on foreign troops.

Günter Katz: “Very sadly, we had two more insider attacks within the last 24 hours. Last, yesterday in the late afternoon, we had an insider attack where a member of the Afghan local police was killing two British soldiers, wounding another British soldier. The shooter has been killed during that incident. In the early morning hours of today, four ISAF [International Security Assistance Force] service members have been killed by members of the Afghan police. This incident is still under investigation, and as soon as we have more findings, we will inform you about that.”

The so-called “green-on-blue” attacks by Afghan forces against foreign troops have claimed 51 lives so far this year, well surpassing the 35 deaths for all of 2011. On Sunday, General Martin Dempsey, the chair of the U.S. joint chiefs of staff, called the violence “a very serious threat” to the occupation, adding: “You can’t whitewash it … Something has to change.”