Chilean police are investigating after a nun, 80, left a suitcase containing the remains of a friend who had been dead for a year on a Santiago street.

The suitcase of bones sparked panic in a city increasingly concerned about violent crime. The nun was later identified from video footage of her, wearing a habit, at the scene.

The woman told police that she and her friend, a fellow nun who died at age 58, had entered into a pact to stay together even after death took one of them.

"There was a pact. The person died a year ago and the other has kept her in a suitcase ever since due to the affection she had" for her friend, police official Juan Fonseca told reporters on Wednesday.

The younger nun had died of illness, and police do not suspect foul play.

A recycler had picked up the suitcase but put it back after smelling a bad odour.

The nun has not been arrested but risks a sanction under public health regulations for not notifying authorities of her friend's death so she could be buried or cremated.

Chilean media said the women did not belong to a formal religious order but had taken private vows.