An international association of Catholic nuns on Tuesday launched a public awareness campaign to combat human trafficking and prostitution during the World Cup in Brazil.

The nuns will use social media, billboards and rallies in host cities to draw attention to the heightened risk of exploitation of sex workers and job-seekers in general.

"The World Cup is a unique occasion to invite everyone to reflect on the value of life," Sister Gabriella Bottani said at a press conference in the Vatican.

Bottani said her association, Talitha Kum -- a Biblical phrase meaning "Little girl, get up!" -- was also conducting training courses to spot signs of trafficking.

The clergywoman said that for previous World Cups in Germany and South Africa, the level of "exploitation" had gone up by 30 percent and 40 percent respectively.

"The majority of trafficked people in Brazil are young women from poor families with low education," she said.

The campaign "aims to inform and raise awareness among the population on possible risks and how to intervene to report possible cases," she said.

Among past and upcoming initiatives will be ads posted on the sides of buses in Manaus, a torch-lit procession in Brasilia, talks in schools in Sao Paulo and handing out pamphlets at tourist hotspots in beach resorts.

Sister Estrella Castalone said that the World Cup was bringing in many workers from neighbouring countries and from rural areas to work in bars or for delivery services.

"People who accept job offers can be tricked and become victims of different forms of exploitation," she said.