Police that the man had complained of tingling in his arm and chest while officers checked his ID in the capital's Mitte district, where thousands of protesters had rallied on Sunday despite an official ban on demonstrations.
About 600 people were detained during the demonstrations, which saw outbursts of violence as protesters defied orders to disperse and tried to break through police lines.
Officers provided first aid to the man until an ambulance arrived and took him to the hospital, where he later died, police said.
An investigation has been opened into the man's death. (...)
