Miami and Bridgeport are demanding compensation for the expense of treating victims of gunshot wounds and investigating gun-related crime.

The BBC's Jane Hughes: One underworld supplier obtained 432 guns in five months

They are following in the footsteps of New Orleans and Chicago which filed similar suits last year.

Bridgeport, Connecticut's largest city, is seeking $100 million from gun makers including the number one US handgun maker, Smith & Wesson Corp.

It alleges that manufacturers have failed to make guns with adequate safety features and been careless in distribution.

"We are saying to the handgun industry, 'From now on, you are responsible for the costs associated with your dangerous products, not Bridgeport's families'," the city's mayor, Joe Ganim, said.

Miami-Dade County in Florida filed a similar suit against 25 gun makers and distributors and three industry associations.

"We will not allow the gun industry to escape accountability any longer," Miami-Dade County Mayor Alex Penelas said. "They have killed our children by the dozens."

"This is about all of the children whose lives have ended at the barrel of a gun.''

Two-year-old victim

Miami-Dade County has logged 763 gun deaths in the past two years. The county's public hospital treats 100 children a year for bullet wounds. Victims include a two-year-old who killed himself while playing with a gun.

The Miami suit does not specify damages, but seeks reimbursement for "hundreds of millions of dollars" in police, paramedic and hospital expenses.

It says gun makers have failed to equip their products with trigger locks, load indicators and other devices to make them safer.

'Not our problem'

Some mayors have predicted up to 50 suits will be filed by the end of this summer.

New Orleans is already suing gun manufacturers, pawnshops and three trade associations, while Chicago is taking action against manufacturers, distributors and dealers.

Officials in Atlanta, Los Angeles and San Francisco are planning similar lawsuits.

Gun manufacturers say they are not responsible for what consumers do with their products. Tobacco companies used a similar argument when individual states sued them for the costs of treating smoking-related diseases.