Outside support for the warring parties in Syria has helped sustain the conflict and transformed it into a proxy battle by regional powers, with Russia, Iran and the Lebanese militant group Hezbollah helping the government and with Saudi Arabia and Qatar providing the main support for the rebels.

But the flow of private funds to rebel groups has added a wild-card factor to the war, analysts say, exacerbating divisions in the opposition and bolstering its most extreme elements. While the West has been hesitant to arm and finance the more secular forces that initially led the turn to armed rebellion, fighters have flocked to Islamist militias and in some cases rebranded themselves as jihadist because that is where the money is.

“It creates a self-sustaining dynamic that is totally independent of all the strategic and diplomatic games that are happening and being led by states,” said Emile Hokayem, an analyst in the Middle East with the International Institute for Strategic Studies.

Most private donors shun the Western-backed Supreme Military Council, undermining a body meant to unify the rebels into a moderate force. And they dismiss the opposition’s political leadership as well as calls by the United States and other powers for peace talks. With funds estimated to be at least in the tens of millions of dollars, they have contributed to the effective partition of Syria, building up independent Islamist militias that control territory while espousing radical ideology, including the creation of an Islamic state.

Rebel fund-raisers have relied heavily on social media. Some have hundreds of thousands of followers on Twitter, where they spread posts calling for donations, announcing drop-off points and listing phone numbers where operators are standing by.