Russia, Iran and Turkey said Thursday that they have agreed to create “de-escalation zones” across four areas in Syria, renewing diplomatic ­efforts to bring warring parties in the country to heel after six years of fighting.

Meeting in the Kazakh capital, Astana, the three powers said the cease-fire deal would come into force Saturday and would apply to both government and rebel forces in the designated areas, where the Islamic State does not hold large swaths of territory.

The agreement, signed by all three guarantor countries, said that the zones would be demarcated by checkpoints on the ground and that “unarmed ­civilians” would be able to move freely between government- and ­opposition-held territory. Checkpoints would be overseen by the three guarantors but could, “if necessary,” be manned by unspecified “third parties,” it said. […]