Donald Trump said on Saturday that the FBI had missed the warning signs of the suspect in the Florida high school shooting because it had been "spending too much time" investigating his campaign's links with Russia.

The Federal Bureau of Investigation has come under pressure in recent days after it admitted it failed to act on a tip off it received about 19-year-old Nikolas Cruz, who is accused of killing 17 people at the Marjory Stoneman Douglas High School.

First it was revealed that the FBI failed to delve into a YouTube comment posted by a "Nikolas Cruz" that said, "Im going to be a professional school shooter." The FBI said it could not determine who made it.

On Friday, the bureau said it had failed to act on a tip that Cruz had a "desire to kill people," disturbing social media posts and access to a gun.

The US President has also faced criticism for not addressing the subject of gun control in the days after the shooting. Survivors of the shooting and relatives of the victims have demanded action after it emerged that Cruz was able to legally buy a semi-automatic firearm despite a history of troubling and violent behaviour.

Mr Trump laid the blame at the FBI and the Democrats in a pair of tweets on Saturday.