Boys as young as six have been filmed at a religious youth group meeting in Sydney's south-west chanting extremist Islamic views and calling for US President Barack Obama to "go to hell".

In the video, uncovered by Channel Seven, four boys said to be aged six to 13 are shown performing on a stage as "Soldiers of Khilafa" or soldiers of the caliphate, waving flags and also chanting for the head of Syrian President Bashar al-Assad.

Abdullah Elmir appears in his latest Islamic State video. Credit:Screengrab

The footage, which has been described by government ministers as "disturbing" and "sickening", shows a six-year-old boy take the microphone and pronounce: "You're never too young to be a Soldier for Khilafa."

The children promise to die fighting to end democracy in Australia, replacing it with a caliphate ruled by Islamic law, Seven claims.