Khaled Sharrouf, a convicted terrorist from Australia, posted a photo of his son, believed to be younger than 10, holding the decapitated head of a Syrian soldier on Twitter, reports the Associated Press. The photo was taken in Raqqa, the eastern Syrian city that the Islamic State has declared the capital of its Islamic Caliphate.

Sharrouf, along with his wife and three sons, had gone to Syria to join the fight against the Assad regime. He was previously convicted for his role in plotting terrorist attacks in Melbourne and Sydney in 2009 and served four years in prison, notes AP. Sharrouf previously posted photos of himself posing with Syrian soldiers' bodies. In the photo of his son, Sharrouf tweeted, "That's my boy!"

Australian Prime Minister Tony Abbott condemned the photo and called ISIS "barbaric," reports Agence France-Presse. "What we've got to appreciate is that Islamic State -- as they're now calling themselves -- is not just a terrorist group, it's a terrorist army, and they're seeking not just a terrorist enclave but effectively a terrorist state, a terrorist nation," said Abbott from the Netherlands.

Abbott is in the Netherlands to discuss the next steps in the MH17 investigation. "I’ll have an opportunity to talk to Prime Minister [Mark] Rutte and his senior officials about just what needs to be done to ensure that the investigation is concluded, the guilty are punished, and justice is delivered to the grieving families of the 298 innocent people who were murdered on Flight MH17," said Abbott in a statement.

Sharrouf's photo also drew the ire of U.S. Secretary of Defense Chuck Hagel, who said ISIS was a "threat." A leader of the Muslim community in Australia also spoke out against the photo. "Even if you are saying to me he made his son lift or carry and take a picture with a decapitated head, this is something reflective of something we can all agree -- this is an act of a lunatic," Samier Dandan, president of the Lebanese Muslim Association, told Australia's ABC.