Civilians around the world hold more guns, handguns and rifles than previously thought, a new survey says.
Some 650 million small arms are reportedly in the hands of civilians
Three times more weapons are held by civilians than by all the world's armies and police forces together, the study from a Geneva-based group says.
The Graduate Institute of International Studies' report calls for greater world co-operation to combat urban gun crime.
Uncontrolled urbanisation is leading to decreased public safety and increased levels of armed violence, it adds.
The survey on the spread of small arms says that out of the 875 million firearms circulating around the world, 650 million are held by civilians - some 200 million more than previous estimates.
What concerns the Geneva-based researchers most is the changing relationship between society and weapons, especially in big cities, says the BBC's Imogen Foulkes in Geneva.
In the vast urban centres of Africa, Asia and Latin America, wealthy citizens are buying guns to protect themselves, while outside the gated communities in which they live, drug-related crime and gang warfare are on the increase, our correspondent adds.
In Brazil's cities, the number of gun-related deaths is higher than that of many countries at war.
The report also calls for more controls on arms sales, pointing out that many of the world's weapons exporters - among them Germany, Italy and the UK - could do more to ensure the guns they sell do end up in the right hands.
Keith Krause, director of the small arms survey, says countries need to be sure the weapons they export go where they are supposed to.
"Here there has been a lot of attention on the sale of American weapons to Iraq to re-equip the Iraqi forces. And the US government accounting office has expressed great concern over the fact that the United States cannot actually account for all of the weapons that they have transferred.
"That doesn't mean they have been lost, but it means we no longer know whether they are still with the people who legally acquired them."