SOCHI, Russia — The Russian hosts of the 2014 Winter Games made clear long ago they would brook no political protests at the Olympics, and now, it seems, they are having second thoughts about allowing dissidents even to attend as spectators.

The Russian Olympic Committee has quietly prohibited several Russian political activists from attending sporting events by denying them documents known as Olympic passports, or fan passes, which spectators need in addition to tickets to gain access to sporting venues.

The passports were required as part of the security precautions for the Games, which will be held in the vicinity of a long-running insurgency. All spectators must register online and then pick up the pass at an airport or a distribution center; a ticket alone will not allow admittance to a sporting event.

But the harassment of the activists seems to go beyond counterterrorism. Since returning to power in 2012, President Vladimir V. Putin has cracked down on all forms of dissent, jailing activists, curtailing public demonstrations and muzzling private news outlets in an effort to contain an opposition movement that blossomed in previous years.