"We designed a bullet-proof backpack at the request of our distributors in the United States after the huge trauma caused by the February shooting in Florida," Snir Koren, CEO of Masada Armor, told AFP on Thursday.

Nikolas Cruz, 19 at the time of the attack, allegedly opened fire and killed 17 people on February 14 in his former high school in Parkland, Florida with a semi-automatic AR-15 rifle.

He has said that he heard voices telling him to "burn, kill, destroy".

Prosecutors are seeking the death penalty for him, in a trial that could begin at the end of next year.

In a matter of months protective gear manufacturer Masada Armor, based in the northern Israeli town of Julis, developed its bullet-proof backpack and got it certified by the Israeli army and police.

"Since then, orders from the United States have been coming in," Koren said in Hebrew.

"In two months we have sold hundreds and are gearing up to increase production rates to 500 units per month."

The basic model, weighs around three kilograms, (six pounds) protects against 9mm pistol fire and sells for $500, he says.

An improved version, weighing five kilograms, is designed to give protection against high velocity rifles such as the AR-15 and the M-16 and Kalashnikov assault rifles and will sell for more than $700.

Koren says that while his bags are suitable for college students, they are too heavy for younger pupils.

"We are developing a lighter model for their type of morphology," he said.

The Parkland massacre -- one of the deadliest mass shootings in recent US history -- sparked a nationwide youth campaign for gun control.

After the shootings, US President Donald Trump said he was open to tighter gun control measures but has opposed a ban on assault rifles, a key demand of the student protesters.

   He has also supported   arming teachers.