By Tom Gibb BBC correspondent in Brazil

A study published in Brazil concludes that more young people below the age of 18 are killed by guns each year in Rio de Janeiro than in many areas of the world formally at war.

The study concludes that there are strong similarities between children involved in drug wars in Rio's slums and child soldiers elsewhere in the world.

Police rarely venture into the slums

Many slums in Rio de Janeiro have long been run by drug barons, often with links to local politicians and police.

The report details how the gangs employ teenagers to guard their domains.

Sometimes they are even given ranks and called soldiers.

The levels of violence are comparable to a war zone.

In the last 14 years, for instance, almost 4,000 under-18-year-olds were killed by firearms in Rio alone.

That compares, the report says, with just under 500 children killed in the fighting between Palestinians and Israelis in the same period.

There are estimated to be between 5-6,000 armed children in Rio.

Most of the killings take place in disputes over territory between drug gangs.

Lawless slums

The report was written by a British anthropologist, Luke Dowdney, in conjunction with Brazilian non-governmental organisations working in Rio's slums.

While it presents testimonies which show the similarities between Rio's teenagers and child soldiers elsewhere in the world, the report makes it clear that this is not the result of a war.

Rather, it is because the authorities have simply abandoned the slums, creating a power vacuum which is filled by the drug gangs.

The report only covers Rio de Janeiro but there are similar levels of violence in other Brazilian cities.

In particular, areas of Sao Paolo have some of the highest murder rates of the hemisphere, although the violence, experts say, is more random and less clearly the result of organised gang warfare.