It is not the first time tensions have flared between the Nusra Front and other revolutionaries.

CNN: How Islamists are gaining ground in Syria

The tensions that flared this week between President Obama and congressional Democrats should not be exaggerated.

CNN: Commentary: Obama and the life of the party

Tensions had earlier flared between the Syrian regime and Turkey after shells fired from Syria landed on the Turkish side, killing five Turks, and prompting Germany, the Netherlands and the U.S. to send two batteries of Patriot air defense missiles each to protect their NATO ally.

NPR: Turkey Says It Won't Be Drawn Into Syria Conflict