Daniel Rosenthal, 58, went missing from Tatchbury Mount Hospital Saturday in Totton during a routine unsupervised walk on hospital grounds, The Sunday Telegraph reported.
"Police are urging members of the public to report any sightings of him by calling 999 and should not approach him, as he is potentially dangerous," authorities said in a statement. "Daniel has been known to visit various areas of the New Forest and Southampton.
Rosenthal was convicted of murdering his mother, Leah Rosenthal, in 1981 and dismembering her body with a hacksaw. He was jailed for life.
Rosenthal was also accused of hacking his father, Milton Rosenthal, to death in Paris and hiding the body in a garbage bag in a forest about 100 miles away from the capital. He wasn't charged with his father's death.
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