Michael Jackson's father Joe (L) and brother Jermaine Jackson leave the courthouse after the reading of the guilty verdict in Dr. Conrad Murray's trial in Los Angeles, November 7, 2011.(FILE)

Jermaine Jackson has spoken out to clear up reports his mother Katherine is missing, insisting the 82 year old is "fine" and "resting up".

A missing persons report was filed at the Los Angeles County Sheriff's Office on Saturday after members of the Jackson clan were unable to get in touch with Katherine for a week.

Jermaine moved swiftly to clear up rumours about the family matriarch, who he says is recovering in Arizona.

In posts on Twitter.com, he writes, "I want to reassure everyone... that Mother is fine but is resting up in AZ on the orders of a doctor, not us... This is our mother and her health is paramount. We are not inventing or plotting anything. We are following doctor's advice. Period."

News of Katherine's disappearance comes just days after Jackson siblings including Jermaine, Randy and Janet fired off a letter contesting the authenticity of their superstar brother Michael's will.

The Jacksons accused John Branca and John McClain of faking legal documents prior to the singer's death in June 2009, and Katherine is believed to be in the middle of the dispute over the family's financial affairs.

Michael's teenage daughter Paris also took to Twitter to ask her followers to contact authorities with any sightings of Katherine.

She tweeted, "Yes, my grandmother is missing. I haven't spoken with her in a week... I want her home now. If anybody sees my grandmother, please call the authorities or this... security number. Thank you so much."