Police in London have launched a campaign urging young men and boys to hand in their imitation firearms.
The advertising campaign features an invisible man handing in a gun
The four-week surrender scheme will allow people to give up guns anonymously, but police may carry out forensic tests on the items.
The campaign targets imitation guns because they represent the largest number of firearms carried on London's streets, a police spokesman said.
About half of the city's gun crime involves imitation firearms.
Replica firearms involved in crimes including robbery have either been converted to fire live ammunition or are so realistic looking that they are indistinguishable from real guns, according to the Metropolitan Police.
An advertising campaign featuring an invisible man has been designed to target 10 to 25-year-old males and their family members, friends or partners.
During the campaign police will also accept other potentially lethal weapons and information about any imitation firearms.
Officers will visit shops to make sure they are following new legislation surrounding the sale of replica guns and test purchases will be carried out at shops suspected of supplying weapons illegally.
Met Police Commissioner Sir Ian Blair said: "Imitation weapons cause fear and distress on our streets and I would urge members of our communities to take this chance to get rid of them.
"Every gun handed in is one less that can be used for violence and intimidation."
The Violent Crime Reduction Act 2006 made it an offence to manufacture, import or sell realistic imitation guns except in limited circumstances.
The maximum sentence for carrying an imitation gun in a public place without reasonable excuse or lawful authority has been increased from six months to 12 months.
This applies to BB guns, blank firing pistols, cap guns, collectibles, airsoft guns, airguns and other items that resemble a gun.