The killings all took part in the Cyberabad area over the past one year.

The arrests follow a separate series of murders of mostly young children and women in the Noida suburb of Delhi, which has shocked the country.

The police commissioner of Cyberabad paraded the three arrested men before a news conference in the city on Monday.

'Liquor addiction'

Commissioner Prabhakar Reddy told reporters that the men have confessed to killing at least nine people by smashing their heads with boulders.

The Noida killings provoked angry scenes

He said all the victims were killed after being robbed for no more than a few rupees in some cases.

Mr Reddy said none except one woman victim was raped, and there was no sexual angle to the other killings.

He dismissed reports that the accused were part of a homosexual gang as "baseless".

Mr Reddy said that police achieved a breakthrough in the case while investigating the grisly murders of two men whose bodies with crushed heads were found lying at a deserted place in an industrial area last week.

'Co-operative'

The other victims included a woman - an alleged prostitute - who were killed after being sexually assaulted.

Meanwhile police investigating the Noida murders in Uttar Pradesh (UP) say that Surendra Kohli, one of the two accused, has undergone various psychological tests at the Gandhinagar Forensic Science Laboratory in the state of Gujarat.

The second accused, Moninder Singh Pandher, is likely to be put through the same tests on Tuesday in Gujarat - one of the few places in India that has such facilities.

Police say their investigations into the Noida killings is still continuing

The two are accused of killing 17 children and women in Noida.

The director of the laboratory Dr JM Vyas stated that the test on Surendra Kohli was carried out over a period of more than seven hours.

He said that the accused was co-operative during the test which involves a drug that makes the subject go into a semi-conscious state.

Mr Pandher was sent to the Gandhinagar Civil Hospital to be kept under medical supervision after complaining of chest pains.

Dr Vyas said that once the forensic experts have finished conducting the tests, it will take several days to analyse the findings.

Police say that the tests are intended solely to assist them in their investigation, and are not submissable as legal evidence.

The Gujarat laboratory is one of the few places in India equipped to carry out such tests.