NEW DELHI: Reports of human trafficking in India increased by 25 percent in 2015 compared to the previous year, with more than 40 percent of cases involving children being bought, sold and exploited as modern day slaves, government crime data showed.

The National Crime Records Bureau (NCRB) said there were 6,877 cases related to human trafficking last year against 5,466 in 2014, with the highest number of cases reported in the northeast state of Assam, followed by the eastern state of West Bengal.

The data released on Tuesday showed 43 percent of the 9,127 victims were below the age of 18. Crimes included inducing a minor girl with intent of sexual intercourse, buying or selling a minor girl for prostitution, and keeping a person as a slave.

Activists attributed the rise in reported cases to greater public awareness as well as increased police training, resulting in better enforcement of anti-human trafficking laws.

However they said the real number of cases could be much higher because many victims, especially those from poor, rural backgrounds, remain unaware of the crime.

"We all know the numbers are very high and we expect the numbers to increase over the years," said Supreme Court lawyer Ravi Kant and founder of Shakti Vahini, a Delhi-based anti-human trafficking charity.

"Increased cases means that law enforcement agencies are now treating the issue of human trafficking seriously."

South Asia, with India at its centre, is one of the fastest-growing regions for human trafficking in the world.

Gangs sell thousands of victims into bonded labour every year or hire them out to exploitative bosses. Many women and girls are sold into brothels.

India, alone is home to 40 percent of the world's estimated 45.8 million slaves, according to a 2016 global slavery index published by the Australia-based Walk Free Foundation.

17,600 Cases awaiting trial

New Delhi police on Tuesday arrested a couple and charged them with trafficking and organised criminal activity, accusing them of trafficking hundreds of young women and girls over many years and selling them to brothels in Delhi's red-light area.

Police said the man, 50, and his wife, 45, had lured the victims, from poor regions such as West Bengal, Jharkhand and Assam as well as neighbouring Nepal, with the promise of good jobs before selling them to brothels for 100,000 rupees each ($1,500).

The NCRB data showed there were 19,717 cases related to human trafficking awaiting trial in 2015, of which 15,144 were cases from the previous year.

Only 2,075 trials were completed -- resulting in 1,251 acquittals and 824 convictions. Over 17,600 cases were still pending trial at the end of 2015, the figures showed.

Activists say although the government response to human trafficking has improved in recent years, justice and support still eludes many victims, especially children.

India has far too few courts, judges and prosecutors for its 1.3 billion people and there is a backlog of million of cases pending before the courts.

The government has introduced an online platform to find missing children, signed bilateral anti-human trafficking pacts with nations such as Bangladesh and Bahrain and authorities are now working with charities to train law enforcement officers.

Prime Minister Narendra Modi's government also plans to unveil India's first comprehensive law on human trafficking.

The Trafficking of Persons Bill, which aims to unify existing laws, prioritise survivors' needs and provide for special courts to expedite cases is expected to be brought before parliament for approval by the end of the year.