Nearly 600 people died in police custody in India between 2010 and 2015, says the US-based Human Rights Watch (HRW) in a new report.

The rights group said no policeman was convicted for a prisoner's death in custody during this period.

India's police routinely attributes deaths in custody to illness, attempted escape, suicide and accidents.

But rights groups say a large number of such deaths happen because of torture in custody, claims officials reject.

On Monday, the rights group released a 114-page report which examines "police disregard for arrest regulations, custodial deaths from torture, and impunity for those responsible".

The report draws on "in-depth investigations" into 17 deaths in custody that occurred between 2009 and 2015, including more than 70 interviews with victims' family members, witnesses, justice experts, and police officials.

In each of the 17 cases, the report says, the police did not follow proper arrest procedures, making the suspect more vulnerable to abuse.

"Police in India will learn that beating suspects to confess is unacceptable only after officers are prosecuted for torture," said Meenakshi Ganguly, South Asia director at Human Rights Watch.

"Our research shows that too often, the police officers investigating deaths in custody are more concerned about shielding their colleagues than bringing those responsible to justice."

By law, every person taken into custody must be medically examined and produced before a magistrate within 24 hours.

Human Rights Watch said the government data revealed that in 67 of 97 deaths in custody in 2015, the police either failed to produce the suspect before a magistrate within 24 hours or the suspect died within 24 hours of being arrested.

The rights group said official investigations to examine wrongdoing rarely find police culpable, and the police also delay or resist filing complaints against implicated police officers.