Jeff Sessions, the US attorney general, has officially proposed a rule that would effectively ban bump stocks, devices that turn semi-automatic weapons into fully automatic weapons.

The announcement comes as thousands of people in the US take part in the March For Our Lives protests which call for stricter gun control.

"After the senseless attack in Las Vegas, this proposed rule is a critical step in our effort to reduce the threat of gun violence that is in keeping with the Constitution and the laws passed by Congress," Sessions said in a statement.

Under US law, machine guns are officially banned. However, semi-automatic rifles, like the AR-15, are legal because of their lower rate of fire.

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Bump stocks use the recoil of these semi-automatic rifles to allow the weapon to fire at a higher rate, effectively turning a semi-automatic into a machine gun.

The new rule would classify bump stocks as part of a "machine gun", making it illegal to buy or sell them.

The weapon modification was heavily criticised last October after one of the deadliest mass shootings in US history.

The attacker, 64-year-old Stephen Paddock, used the modifications to increase his rate of fire, allowing him to kill 58 people at a concert in Las Vegas.

The proposal comes after President Donald Trump announced in February that he was in favour of the ban following a mass school shooting in Florida.

Following the attorney general's announcement, Trump reiterated his support for the plan on Twitter, saying "we will ban all devices that turn legal weapons into illegal machine guns".

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Bump stocks were not used during that incident, but calls, led by students, for stricter gun control have been heard nationwide.

That call for stricter gun control has not died down since then, leading to Saturday's rallies across the US and around the world in which thousands of people take part in the March for Our Lives rally.

The protest is led by survivors of last month's shooting at Florida's Marjory Stoneman Douglas High School, where 17 people were killed after a former student allegedly went on a shooting rampage inside the school.

Students, under the banner #NeverAgain, are demanding that Congress pass a law banning assault weapons, halt the sale of high-capacity magazines to restrict access to ammunition and tighten the background check process.

They are also calling for a bipartisan effort to ramp up gun control and demanding "a comprehensive and effective bill be immediately brought before Congress to address these gun issues".

Saturday's march comes off the back of the National School Walkout earlier this month when thousands of students and teachers walked out of the classroom for 17 minutes to remember the victims of last month's shooting and demand stricter gun control.