On Valentine's Day evening, people stood outside for 15 minutes. They used the flashlight function on their smartphones and arranged candles in the shape of a heart.
The action went ahead under the motto "Love is stronger than fear."
Organizers described it as a response to the "unprecedented wave of violence and repression" by security forces at past rallies in support of Navalny.
Navalny was arrested last month on his return from Germany. He was being treated there for poisoning with what many Western countries say was a nerve agent developed by the Soviet Union.
The 44-year-old was jailed on February 2 for violating parole on what he said were trumped-up charges.
Supporters of Navalny have attended mass demonstrations in large numbers across Russia in recent weeks.
However, the rallies have resulted in mass detentions of thousands.
Sunday's decentralized and particularly peaceful initiative is meant to make it difficult for the police to take action against it.
Russian law enforcement agencies warned on Thursday that people taking part in unsanctioned rallies could face criminal charges.
President Vladimir Putin suggested that the recent wave of protests across Russia had been stoked by his opponents abroad against the backdrop of the widespread "exhaustion, frustration and dissatisfaction" arising from the coronavirus pandemic.
"Our opponents or potential opponents have always ... relied on very ambitious, power-hungry people and have always used them," the president said in an interview with Russian media conducted on Wednesday and broadcast Sunday by the public Rossiya 24.