Russia's most-wanted terrorist, Doku Umarov, has called a halt to attacks on civilians in Russia while anti-government protests continue.
His announcement came on the eve of another large-scale protest in Moscow, planned for this afternoon.
Insurgents from the Caucasus have been behind some horrific attacks within Russia over the past decade, including the Beslan school siege and numerous suicide bomb attacks on the Moscow underground rail system.
After taking responsibility for a suicide attack on the arrivals hall of Domodedovo Airport in the capital last January, Umarov, a Chechen insurgent leader who styles himself the "Emir of the Caucasus", promised a "year of blood and tears" for Russia.
But in yesterday's surprise announcement, he said his Caucasus Emirate movement would cease all attacks on civilian targets. "If the peaceful population does not take part in the war against Islam, our religion tells us to take care of the peaceful population and not to touch them," Mr Umarov said in a video message. He explicitly linked his decision to the protests, saying: "Today's events ... show the population of Russia doesn't support Putin. Therefore, I order all groups who are carrying out or plan to carry out special operations on the territory of Russia to limit them if the peaceful population will suffer."
The insurgency in Russia's troubled southern provinces has changed in the past decade from a largely secular Chechen nationalist cause to a movement with more radical Islamist goals, but the main grievances behind most who join its ranks are still the harsh methods used by Russian forces and their proxies in the region. Mr Umarov said police and government officials would remain targets.
The war in the Caucasus is far from the minds of Russia's nascent middle class, who have been the vanguard of the protest movement, and Mr Umarov's statement, suggesting that the terrorists and protesters have similar goals, may even play into the Kremlin's hands. Being linked with a rebel movement for which few Russians have any sympathy will not be good for protest leaders.
The turnout at today's rally, the first since the long new year holidays, will be a good indication of whether the movement that brought tens of thousands out on the streets in December was a flash in the pan, or the start of a sustained challenged to Vladimir Putin.