Afghan Grenade Wounds American Soldiers as Riots Still Rage KABUL, Afghanistan - A grenade thrown by Afghan protesters wounded at least six American service members in northern Afghanistan on Sunday, officials said, as new details emerged in the investigation of the shooting death of two American officers within the Interior Ministry building the day before. Rioting continued across the country on Sunday as anger over the burning of Korans by the American military continued unabated, putting the relationship between Afghanistan and the United States on shaky new ground. At least one Afghan was killed in clashes with the Afghan police. A few details of the killing within the Interior Ministry were emerging, although many reports offered conflicting views of what had happened. According to three Afghan security officials familiar with the case, the main suspect was Abdul Saboor, who was said to have worked in the ministry for more than a year as a driver. The two American officers who were killed were shot in the head and the pistol used to kill them was equipped with a silencer, the officials said. Afghan officials said that Mr. Saboor was at large, apparently able to leave the ministry without complication after the shooting. That suggested to some observers that he may have had help in the attack. President Hamid Karzai called for calm during a televised news conference Sunday from the presidential palace. It was a time for self-restraint, he said, "so that it does not provide an opportunity for the enemy to take advantage." In his address, President Karzai did not comment on the shooting of the two officers, saying, "It is not yet clearly known as to who has committed this and where was he from, whether Afghan or foreigner or any other element involved, so we can not make any comments at this point. " But he said he understood the decision by NATO to withdraw its advisers from all Afghan ministries the day before. That pullout of advisers cast immediate doubt on one of the most critical parts of the international mission in Afghanistan: the close mentoring and training of Afghan security forces who would take over responsibility for securing the country and fighting the Taliban after the United States pulls its combat troops out of the country. The killings, which happened in the national police coordination center or possibly in a nearby office in the same area, were in the most tightly secured part of the ministry where only a select group of security-cleared officials were allowed. It was not clear how a person who was relatively low in the hierarchy could have entered the area and shot the two Americans. Violence by Afghan security personnel, or sometimes by Taliban infiltrators wearing uniforms, against NATO forces in the country had already been on the rise before the Koran burning ignited nationwide protests and a wave of new attacks.The injuries to American service members on Sunday were inflicted after protesters threw a grenade at a camp in the northern city of Kunduz, where the American military has a mentoring program with the Afghan national police., said Mohammed Ayob Haqyar, the district chief of Imam Sahib District where the base is located. NATO said an explosion took place outside the base, injuring several military personnel who had to be airlifted out, but that the base had not been breached. It also said the explosion was followed by small-arms fire. About 4,000 protesters massed in the city on the sixth day of protests around Afghanistan since first reports of the Koran burning at another NATO base appeared last week. One protester was killed in clashes with the police on Sunday. In Samangan Province, an initially peaceful protest of about 3,000 people turned violent when the police barred the protesters" way, according to the provincial governor's office. The Koran burnings and the subsequent unrest is complicating relations between the United States and the Afghan government at a time of critical negotiations, including the future of the main American prison in Afghanistan, and future cooperation between Afghanistan and the United States after the 2014 deadline for an American troop withdrawal. Secretary of State Hillary Rodham Clinton on Sunday expressed regret for the incident involving the Korans but said it should not derail the American military and diplomatic effort in Afghanistan. "We are condemning it in the strongest possible terms," she said in Rabat, Morocco, "but we also believe that the violence must stop, and the hard work of trying to build a more peaceful, prosperous and secure Afghanistan must continue." Meanwhile, Ambassador Ryan Crocker, the United States ambassador to Afghanistan, told CNN that the assassination of the two American officials would not lessen America's commitment to the region. This is not the time to decide we're done here. We've got to redouble our efforts," he said. If we decide we're tired of it, Al Qaeda and the Taliban certainly aren't.