Shipman may be among world's worst serial killers

Estimates that Harold Shipman may have murdered 297 patients during his 24-year career as a doctor make him one of the world's most prolific serial killers.

The worst known serial killer was an Indian man called Behram, who strangled at least 931 victims with his yellow and white cloth strip, or ruhmal, in the Uttar Pradesh district of India between 1790 and 1840.

Transylvanian Elizabeth Bathory is thought to be the most prolific female murderer. She is believed to have killed about 650 girls between 1560 and 1615 in order to drink their blood and bathe in it, an act which she was convinced would preserve her youth.

The most prolific known modern serial killer is Colombian Pedro Lopez, who raped and killed at least 300 young girls in a killing spree through Columbia, Peru and Ecuador during the 1970s.

Lopez - dubbed the Monster of the Andes - was exposed in 1980 after a flash flood uncovered the first of his victims. He was sentenced to life imprisonment in Ecuador later that year, after 50 more graves were uncovered.

In 1999, fellow Colombian Luis Alfredo Gavarito confessed to having raped, tortured and murdered 140 children in a five-year killing spree.

The mutilated corpses of 114 mostly male victims aged between eight and 16 were uncovered near more than 60 towns in at least 11 of Colombia's 32 provinces. The bodies were beheaded and bore signs of having been tied up.

Among the most prolific of British murderers was Mary Ann Cotton, who was hanged in Durham prison in 1873.

She married three times and over 20 years used arsenic to poison as many as 21 people - husbands, children, step-children, friends and relatives. Her motives were either insurance money, re-marriage or spite.

She was executed after being arrested following a spate of deaths at her home in County Durham in the 1870s.

Edinburgh body-snatchers Burke and Hare became serial killers after identifying the lucrative market for selling human bodies with no questions asked to the city's medical schools.

The labourers from Ulster strangled people in Edinburgh's old town and sold the bodies but the murder of their 16th victim led to their arrest and Hare turned King's evidence, which sent Burke to his death on the gallows in January 1829. Hare is said to have died a pauper in London in 1859.

In December 1978, Dennis Nilsen began a killing spree and confessed to being responsible for the deaths of 15 or 16 young men in north London over a four-year period.

He often plied his victims with drink before strangling them - often with a tie - before dissecting their bodies with a knife.

Nilsen used a cooking pot to boil some victims' heads. The motive for the killings was thought to have been revenge after the man he loved walked out on him. He was given eight life terms for six murders.

Yorkshire Ripper Peter Sutcliffe preyed on prostitutes and young women in the Leeds area. His five-year reign of terror left 13 dead and started in October 1975 when he beat a prostitute around the head and stabbed her 14 times. It led to one of the most complex and lengthy manhunts for years.

Sutcliffe was interviewed by detectives nine times but was only picked up over a routine inquiry. He was jailed for life in 1981 and later transferred to Broadmoor special hospital.