Miami (AFP) - The Republican governor of Florida called Friday for a police officer to be assigned to every public school in the state, and for the minimum age for gun purchases to be raised from 18 to 21 in the wake of the Parkland mass shooting.

"I'm calling for a mandatory law enforcement officer in every public school," Rick Scott told a news conference, as he unveiled a raft of safety measures in response to last week's deadly rampage.

Scott said the southern US state "will require all individuals purchasing firearms to be 21 or older," and intended to make it "virtually impossible" for anyone with "mental issues" to acquire a gun.

Students who survived the February 14 shooting at Marjory Stoneman Douglas High School have stepped up pressure on the governor to take action to protect their schools, demanding stricter gun control laws.

The self-confessed gunman, 19-year-old Nikolas Cruz, legally purchased the AR-15 semi-automatic assault rifle used to killed 17 people at the Parkland, Florida school.

Scott, a Republican endorsed by the National Rifle Association, said the package of measures had been designed after meetings he held with some students.

The measures do not include a ban on semi-automatic assault weapons like the AR-15.

Instead, the state would raise the minimum age for all gun purchases to 21 from 18, and ban the purchase or sale of so-called "bump stocks," devices that enable semi-automatic weapons to fire at rates akin to machineguns.

The plan calls for deploying a police officer for every 1,000 students in every public school in Florida from the start of the 2018 school year.

An additional $50 million would be made available for mental health initiatives.

US President Donald Trump on Tuesday also called for a ban on bump stocks.

The devices were used by Las Vegas shooter Stephen Paddock, who killed 58 people at an outdoor concert October 1.