The funeral for Russian opposition leader Alexei Navalny has taken place in Moscow.

The service was held on Friday under heavy security, with Navalny's parents and other relatives in attendance.

Crowds gathered outside the church chanting his name and expressing gratitude to the vocal critic of President Vladimir Putin.

Security forces and police set up fences, but no major clashes have been reported.

A spokesperson for Navalny's support group said his body will be laid to rest at a nearby cemetery.

Navalny was reported to have died in an Arctic prison colony on February 16.

Speculation is growing that the Putin administration was responsible for his death.

The G7 leaders issued a statement in February urging Russia to clarify the circumstances.

Authorities are apparently on high alert for the possible spread of anti-government moves triggered by the funeral.

Presidential spokesperson Dmitry Peskov said, "any unauthorized gatherings will be in violation of the law" and "those who participate in them will be held responsible."