A UK-based children's charity said Friday it will expand an anti-human trafficking project in the Philippines, as fears grow that young survivors of Super Typhoon Haiyan are becoming easy prey.

Haiyan left nearly 8,000 people dead or missing in one of the worst natural disasters to hit the Philippines, flattening entire towns and displacing more than four million people.

"Experiences from similar disasters show that the potential for human trafficking, particularly of women and children, increases after a humanitarian crisis such as Typhoon Haiyan," Plan International country director Carin van der Hor said in a statement.

The charity is therefore extending its project, first launched in 2005, for another two years, with a focus on the disaster zone.

Under the plan it will work with the government to raise awareness in communities affected by Haiyan to help residents understand the risks of trafficking within and outside the Philippines, van der Hor said.

Plan will also help the government boost monitoring efforts at airports and seaports where trafficked women and children may be removed from the country or sent to large cities.

Nearly a week ago the charity raised concerns about the recruitment of suspected child workers from the central island of Samar, one of the areas worst-hit by the typhoon.

It said five high school girls were sent to work in Angeles, a northern Philippine city that has a large red light district, following the disaster.

The Philippine government has said it is investigating the recruitment of the girls.

Samar, the country's third-largest island, is an impoverished, largely rural region wracked by a communist insurgency that has traditionally supplied young men and women to work as maids and construction workers to more economically vibrant parts of the country.

A 2013 US State Department report on global human trafficking described the Philippines as "a source country, and to a much lesser extent, a destination and transit country for men, women and children subjected to sex trafficking and forced labour".

On Thursday British, Australian and Philippines police said they had dismantled a paedophile ring that streamed live sexual abuse of Filipino children as young as six over the Internet, with victims' parents involved in some cases.

Van der Hor said Plan has worked with the social welfare ministry in the Philippines since 2005 to prevent trafficking and protect as well as rehabilitate survivors.