WASHINGTON: The most powerful pro-gun lobbying group in US is suggesting that armed police be deployed to every school in the country following a mass shooting that left 20 young children dead.

The National Rifle Association, which supports a broad interpretation of US citizens' constitutional right to bear arms, had been under pressure to respond in the wake of last week's massacre in a Connecticut elementary school.

Even as the NRA leaders made their combative and determined appearance, another four people died in Pennsylvania in America's latest shooting spree, including the alleged shooter.

And a string of celebrities including Jeremy Renner, Gwyneth Paltrow and Beyonce launched a video to back a campaign to clamp down on gun sales following the Newtown school massacre.

But the pro-gun lobbyists ceded no ground to those calling for tougher gun laws.

“The only thing that stops a bad guy with a gun is a good guy with a gun,” declared NRA vice-president Wayne LaPierre Friday, in his first public comments since the shooting at the Sandy Hook Elementary School in Newtown, Connecticut.

“I call on Congress today to act immediately to appropriate whatever is necessary to put armed police officers in every single school in this nation,” he said, in a lengthy statement. He took no questions from reporters.

LaPierre said the NRA was ready to help train security teams for schools and work with teachers and parents to improve security measures, and accused the media and the political class of demonizing gun owners.

Last Friday, a troubled 20-year-old man burst into the Sandy Hook school and gunned down 20 six- and seven-year-old children and six staff members trying to protect them, before taking his own life. He also fatally shot his mother.

As LaPierre and his allies were on stage in Washington on Friday, police in Pennsylvania shot dead a man who had killed three people and wounded “several”others.

These deaths were the latest in a series of mass shootings in the United States this year, and prompted President Barack Obama to throw his weight behind plans to revive a ban on assault weapons.

America has suffered an epidemic of gun violence over the last three decades including 62 mass shooting incidents since 1982. The vast majority of weapons used have been semi-automatic weapons obtained legally by the killers.

There were an estimated 310 million non-military firearms in the US in 2009, roughly one per citizen, and people in America are 20 times more likely to be killed by a gun than someone in another developed country.

But LaPierre insisted gun ownership is not the problem.

“You know, five years ago after the Virginia Tech tragedy when I said we should put armed security in every school, the media called me crazy,” he said, referring to a 2007 campus shooting that left 32 people dead.

“But what if, what if when Adam Lanza started shooting his way into Sandy Hook Elementary School last Friday, he'd been confronted by qualified armed security?” he demanded.

“Will you at least admit it's possible...that 26 innocent lives might have been spared that day? Is it so abhorrent to you that you'd rather continue to risk the alternative?”

The statement immediately drew criticism from supporters of tougher gun control, who are pushing to ban semi-automatic assault weapons like the .223 Bushmaster rifle that Lanza used in Friday's shooting.

“The NRA leadership's drive to fill our schools with more deadly guns and ammo is wildly out of touch with responsible gun owners and the American public,” New Jersey Senator Frank Lautenberg said.

The New York Times, in an editorial Saturday, did not mince words, calling LaPierre's remarks a “mendacious, delusional, almost deranged rant.”

One of the protesters, who attempted to drown out LaPierre's statement, bore a banner reading “NRA kills our kids” the other “NRA has blood on its hands.” They were led away by security.

Hollywood stars including Julianne Moore, Jamie Foxx and Jon Hamm meanwhile recorded a video backing a campaign calling notably for a ban on assault weapons, as well as criminal background checks for every gun sold.

“Columbine. Virginia Tech. Tucson. Aurora. Fort Hood. Oak Creek. Newtown. Newtown. Newtown,” they intone in the black-and-white video, taking turns to list the names of America's worst gun massacres of recent years.

“How many more? How many more colleges? How many more classes? How many more movie theaters? How many more houses of faith? How many more shopping malls?” they add in the video on the “Demand a Plan” campaign website.