TROY, Mich. — Republican president candidate Rick Santorum accused President Obama of “showing weakness” in responding to the killings of U.S. servicemen by their Afghan military allies.

After two U.S. soldiers were killed by a man in an Afghan army uniform earlier this week, Obama apologized for the U.S. role in a Koran-burning incident that set off violence and protests in Afghanistan.  Now, two more American officers have been killed in an attack inside the Afghan interior ministry.