There are nine guns for every 10 people in the United States, with about 270 million firearms in circulation, according to a report released Tuesday.

Worldwide, civilians now have access to 650 million small arms — from handguns to semiautomatic rifles — an arsenal that far outstrips what is held by police and militaries, according to the annual Small Arms Survey. It estimates that civilians account for about three-fourths of the 875 million such weapons in circulation.

"Civilian holdings of weapons worldwide are much larger than we previously believed," the director of the Geneva-based group, Keith Krause, told reporters.

But it is the United States that has the heaviest concentration of firearms.

Of the 8 million new firearms manufactured annually around the world, roughly 4.5 million are bought in the United States.

Other countries with high per capita ownership include Yemen, with 61 small arms per 100 people; Finland with 56; Switzerland with 46 and Iraq with 39.

Much lower on the scale are Brazil, with nine guns per 100 people, England and Wales with six, India with four, China with three and Nigeria with one.

The report notes that only about 12 percent of all weapons worldwide are registered with authorities, making it difficult to collect exact data on gun possession. Five years ago the group estimated a total of 640 million small arms worldwide.

"There's a large number of states in the middle, mostly northern industrial states in Western Europe and North America," said Krause, citing France, with 32 per 100 people; Canada and Sweden, with 31 each and Germany, with 30.

The figures dispel the idea that gun ownership and high levels of violence necessarily go hand in hand, he said.

"There's no clear relationship between more guns and higher levels of violence," Krause said, pointing to low ownership and high crime rates in Latin America.

He said studies had shown that gun violence often occurred in places undergoing rapid urban growth, and when lawless areas are created by extreme poverty and the absence of effective policing.

The problem is worsened when members of government or police forces sell ammunition on the black market, Krause said.

In Rio de Janeiro, "a combination of factors suggest that state security forces — most notably the police — are the source of much of the assault rifle ammunition in the hands of criminal gangs," the report said.

Thousands of arms supplied to Iraq by the United States are believed to have been acquired by insurgents through rogue elements in the Iraqi security forces.

Sudan, meanwhile, has purchased more than 25 million firearms in recent years — mostly from China and Iran — despite well-documented human rights violations committed by government-backed militias.

Krause said wealthy countries with lower crime rates, such as those in the 27-nation European Union, are dealing with an increased flow of small arms across borders where controls have been loosened.

Recent shootings in Britain — where ownership is severely restricted and the gun crime rate is low — highlight the need for greater police cooperation in Europe, he said.