"We are certain that foreign interference, terrorist and suspicious measures which have targeted the resilient Syrian people are doomed to fail," the website of the state television network, Press TV, quoted Foreign Ministry spokesman Ramin Mehmanparast as saying.
"The attack has been carried out in order to create chaos and instability in Syria and its perpetrators are trying to block the way to a peaceful resolution," he said.
Iran's parliament blamed the United States and other Western countries for arming and training what it described as "terrorists", the Iranian state news agency reported on Monday.
Images of the bloodied bodies of children after the onslaught on Houla on Friday triggered shock and outrage around the world and underlined the failure of a six-week-old ceasefire plan to stop the violence in Syria.
Iran has voiced support for the U.N.-sponsored peace plan that calls for the withdrawal of troops from residential areas where they have been used to try to crush a 14-month uprising against Syrian President Bashar al-Assad's rule. But Iran says it will not back calls for Assad to step down.
While Iran has supported popular uprisings that removed longtime leaders in Egypt, Libya and Yemen, it has steadfastly supported Syria, a rare ally in the Arab world which is largely suspicious of Shi'ite Iran's ambitions for greater regional influence.
The U.N. Security Council on Sunday condemned unanimously the killings in Houla, which the Syrian government and rebels have blamed on each other.