TOKYO (AFP) - A Peruvian being held in Japan over a suspected killing spree is thought to be the brother of a man dubbed "The Apostle of Death," considered Peru's most prolific mass murderer.

Vayron Jonathan Nakada Ludena, 30, is unconscious in a hospital with a broken skull after falling from the second floor of a house while being pursued by police, local Japanese media reported.

Nakada Ludena is the prime suspect after six people were found stabbed to death in a residential neighbourhood near Tokyo, police said Thursday.

Police believe Nakada Ludena killed 41-year-old Miwako Kato and her two daughters, aged 10 and seven, after their brutalised bodies were found stuffed into two closets in their home in the usually quiet suburb of Kumagaya, north-east of Tokyo.

They also fear he was responsible for the death of 84-year-old Kazuyo Shiraishi, whose body was reportedly found in a bathtub in her home around 100m away hours earlier.

On Monday, police found a couple in their 50s, Minoru and Misae Tasaki, stabbed to death at their house in the same neighbourhood.

Nakada Ludena is believed to have killed the people randomly after he fled from a police station where he was being questioned on Sunday, after being found in an incoherent state in a fire station, local media reported.

Police issued an arrest warrant against him on charges of trespassing after he ran into the residential neighbourhood, the Mainichi Shimbun newspaper and other media reports said.

According to sources in identity records offices in Peru, Nakada Ludena is the sibling of Pablo Nakada Ludena, who killed 25 people in Peru between 2000 and 2006.

Pablo Nakada Ludena, 42, has been diagnosed with paranoid schizophrenia and has attempted suicide. He has been held in a psychiatric prison east of the Peruvian capital Lima since 2007.

In 2011, he told television reporters from behind bars: "I am not a criminal, I'm a cleaner, I got rid of homosexuals and the homeless from society. I killed 25 people to clean the world of scum."