The two Islamist fighting forces in Syria affiliated with al-Qaida on Tuesday appeared to be on the edge of an all-out conflict, with the Islamic State of Iraq and Syria declaring war on all other factions in the Syrian resistance Tuesday with a blood-curdling statement that urged fighters to “show no mercy” in their 5-day-old conflict.

“We have armies in Iraq and Syria full of hungry lions, who drink their blood and consume their flesh, and they find nothing tastier than the blood” of the groups now fighting ISIS, said Abu Muammad al-Adnani, the ISIS spokesman.

The statement, in an audio recording posted to YouTube, came on the heels of a firm but measured declaration of resistance by Jabhat al Nusra.