Guardian has an article (Syria crisis: al-Qaida fighters revealing their true colours, rebels say) in which it writes that there is increasing tension between Al Nusra and the FSA. Some quotes:
Over the past six weeks a once co-operative arrangement between Aleppo's regular Free Syrian Army units and al-Nusra has become one of barely disguised distrust.
A week of interviews with rebel groups in north Syria has revealed a schism developing between the jihadists and residents, which some rebel leaders predict will eventually spark a confrontation between the jihadists and the conservative communities that agreed to host them.
Some already talk of an Iraq-style "awakening" – a time in late-2006 as when communities in the Sunni heartland cities of Fallujah and Ramadi turned on al-Qaida groups in their midst that had tried to impose sharia law and enforce their will through the gun barrel.
"We'll fight them on day two after Assad falls," a commander said. "Until then we will no longer work with them." In recent weeks Liwa al-Tawhid and other militias who form part of the Free Syrian Army have started their own operations, without inviting al-Nusra along.
"They see stealing things that used to belong to the government, like copper factories, or any factory, as no problem," said the rebel commander. "They are selling it to the Turks and using the money for themselves. This is wrong. This is money for the people." On Monday al-Nusra units went to a state-owned water factory on the Euphrates river. They invited regular rebel units to go with them as they picked through parts inside the factory for selling to whoever wanted them. One unit did join the jihadists. Others refused.
Another rebel approached, this time to complain that young girls in his village had been pledged as brides to anyone who joined al-Nusra. "This is part of the employment benefits," he said. For now, community leaders seem to be able to say no to al-Nusra suitors who come calling, but fear these rights might be whittled away if the group consolidates its influence.