Long lines of people, some holding flowers, were forming in Moscow on Friday for the funeral services for Aleksei A. Navalny, Russia’s most prominent opposition figure, two weeks after his mysterious death in a remote Arctic penal colony.

Hours before the planned mourning rites, Mr. Navalny’s family had not received his body from a Moscow morgue, a spokeswoman said. But the body was eventually handed over around 12:30 p.m. local time, she said.

Planning for the service was taking place under pressure from the Russian authorities, who have arrested hundreds of mourners at memorial sites since Mr. Navalny died. Police presence was heavy around the church where funeral services were due to take place on Friday afternoon.

The services were being held at the Church of the Icon of the Mother of God Soothe My Sorrows, a Russian Orthodox church in southern Moscow. Images on social media showed attendees lining up, but also security cameras that the local news media reported had been recently installed, and signs forbidding mourners to take pictures or video in the church.

Still, Ivan Zhdanov, who, like many of Mr. Navalny’s closest associates, is in exile outside Russia, encouraged people to come to the church, saying that the police had not been arresting mourners, as many had feared.

“People are coming to say farewell, and no one is touching them,” Mr. Zhdanov said. “Those who want to come to say farewell can do so.”