The conversations between Mr. Nemtsov and friends included a fair bit of rude street language, and some unguarded asides about some of his fellow protest organizers.
Reached by phone, Nemtsov said he had no doubt that the Kremlin was behind the "absolutely illegal and unconstitutional" intrusion into his private space.
"This is a provocation, not against me, but against our rally on Dec. 24. Putin and (acting Kremlin chief of staff Vladislav) Surkov are terrified that the protest momentum is building, and many more people are going to come out," Nemtsov says. "The goal of publishing my private conversations is to split the opposition."
Nemtsov says he has apologized personally to fellow organizers whom he'd mentioned in disparaging terms, and that he will launch a lawsuit against Lifenews.ru and others who violated his privacy.
"But if they wanted to divide the opposition, the result is the opposite," he adds. "We are more unified than ever, because people are furious at the tactics being employed by the Kremlin. No one can accept these criminal methods."
Another worrisome case involves Sergei Udaltsov, leader of Left Front, a coalition of leftist groups that has applied repeatedly and been refused official registration as a political party.
Mr. Udaltsov, a veteran street activist, has been detained by police more than 100 times in the past five years, mostly for participating in peaceful but unsanctioned political protests. But on the morning of Dec. 4, Duma election day in Russia, he was arrested while walking on the street in what appeared to be a preemptive police operation. He was handed a five-day prison sentence after two police officers testified that he had ignored their advice about where he may cross the street – in other words, alleged jaywalking.