Nearly 46 million people are living in slavery, according to a new report, with India housing the most slaves (18.3 million) while North Korea has the highest prevalence - 5 percent of its total population - of those living in slavery.

The numbers come from the third Global Slavery Index, released Tuesday by the Walk Free Foundation (WFF), an Australia-based human rights organization.

WFF increased its estimate of "people born into servitude, trafficked for sex work, or trapped in debt bondage or forced labor" to 45.8 million from 35.8 million in 2014, according to a report.

"I believe in the critical role of leaders in government, business and civil society," WFF founder Andrew Forrest, an Australian billionaire, said in a statement. "Through our responsible use of power, strength of conviction, determination and collective will, we all can lead the world to end slavery."

Actor Russell Crowe, who hosted the launch of the Global Slavery Index in London Tuesday, spoke about people "in our communities who are stuck, utterly helpless and trapped in a cycle of despair and degradation with no choice and no hope."

"As an actor, my role is often to portray raw human emotion, but nothing compares with the people's lives reflected in the report published today," he said. "The shock of reading the Global Slavery Index was one that I wouldn't step away from."

India was followed by China, with 3.39 million slaves, Pakistan (2.13 million) and Bangladesh (1.53 million), according to the Index. 

The countries with the lowest rates of slavery (0.02 percent or fewer of the population), according to the WFF, are Luxembourg, New Zealand, Ireland, Norway, Denmark, Switzerland, Austria, Sweden, Belgium, Australia, Canada, Spain, Britain, France, Germany and the United States.

Despite India's placement as the leader in overall slavery, the foundation noted that the country had made "significant progress," including measures like tougher penalties for child prostitution and forced marriage, in addition to improved efforts to protect victims of slavery.

The new Global Slavery Index also pointed out "significant progress" made by other countries since 2014, when the previous report was released.

The foundation defines a slave as "a person [who] cannot refuse or leave because of threats, violence, coercion, abuse of power or deception, with treatment akin to a farm animal."