Updated

"De-escalation zones" set up in a deal between Russia, Turkey and Iran in mostly opposition-held parts of Syria have gone into effect.

The plan is the latest international attempt to reduce violence in the war-ravaged country, and is the first to envisage armed foreign monitors on the ground in Syria. The U.S. is not party to the agreement and the Syrian rivals have not signed on to the deal. The armed opposition, instead, is highly critical of the proposal, saying it lacks legitimacy.

The plan's details will be worked out over the next several weeks. It went into effect at midnight Friday.