WASHINGTON (AP) — Republican presidential hopeful Rick Santorum criticized President Barack Obama's apology for the burning of Qurans in Afghanistan, adding that Afghanistan should apologize to the U.S. for the deaths of four U.S. soldiers during six days of violence sparked by the incident.

"There was nothing deliberately done wrong here," Santorum said Sunday on ABC's "This Week". "This was something that happened as a mistake. Killing Americans in uniform is not a mistake. It was something that deliberate."

More than 30 people have been killed in clashes since it emerged Tuesday that copies of the Muslim holy book and other religious materials had been thrown into a fire pit used to burn garbage at Bagram Air Field, a large U.S. base north of Kabul. Protesters angry over Quran burnings by American troops lobbed grenades Sunday at a U.S. base in northern Afghanistan and clashed with police and troops in a day of violence that left seven international troops wounded and two Afghans dead.

"The response needs to be apologized for by (President Hamid) Karzai and the Afghan people for attacking and killing our men and women in uniform and overreacting to this inadvertent mistake," Santorum said on NBC's "Meet the Press". "That is the real crime here, not what our soldiers did."

The president's apology suggests that there is blame and that the U.S. did something wrong "in the sense of doing a deliberate act," Santorum said.

Santorum says that rather than saying he was sorry, Obama should have only acknowledged that burning copies of Islam's holiest book in a trash pit was wrong and taken responsibility for the incident, "but to apologize, I think, lends credibility that somehow or another that it was more than that."

Santorum is the latest Republican to criticize Obama for apologizing for burning the religious materials. Despite apologies from the president and other U.S. officials for what they said was a mistake, their regrets have not quelled the anger of Afghans, who viewed the Quran burnings as an illustration of what they perceive as foreign disrespect for their culture and religion.

Santorum was interviewed Sunday on ABC's "This Week" and NBC's "Meet the Press."