The monkey-man, who is between four and five feet tall, has a "monkey like face", and strikes between midnight and 4am, has pounced on almost 20 victims during the past five days, leaving them with deep scratch marks and gouges on their arms and necks.

The police have received complaints from people sleeping on roofs or in the open near the city's slums. He is also elusive, slipping away into the darkness after his attacks.

Some victims say he wears a helmet; others insist that he sports metal claws, has a shaggy black hide - and possibly roller-skates. At least one man has died after tumbling off a building in panic when his neighbour cried: "The monkey man is here!"

Despite the sightings, however, police remain unsure whether he is, in fact, a monkey.

"We contacted Delhi zoo authorities and the experts say that no simian would ever attack without provocation," Suresh Roy, Delhi's joint police commissioner, said. "We have conducted medical examinations of the victims and nothing concrete has been found.

"Doctors say the bites are animal bites and not of a human," Mr Roy said. "But then there are some people who have also said that the person uses iron claws and teeth."

The monkey-man began his reign of terror at the weekend in the poor colonies of east Delhi. He has since struck so many times across the capital that some officers now believe that there could be more than one monkey man.

Youths armed with axes and sticks, meanwhile, have started patrolling the streets, and rightwing Hindu activists have taken up strategic positions with swords and scimitars.

"The creature had its hands on my thighs when I woke up. It looked like a langur [a type of monkey]," Younus, who lives in the suburb of Krishan Nagar said last night. "When Rehena, my mother, picked up a broomstick, it jumped out of the balcony."

Delhi residents, it seems, are not the first victims of this phenomenon. A "scratcher" known as Springheel Jack appeared in London in 1837. He, too, had iron-clad fingers, glowing eyes, wore dark clothes and scratched his victims. He was never found.