The Federal Bureau of Investigation said on Friday it had failed to act on a tip warning that the man now accused of killing 17 people at a Florida high school possessed a gun, the desire to kill and the potential to commit a school shooting.

The disclosure sparked angry disbelief from residents of the Miami suburb of Parkland still reeling from Wednesday's massacre, the deadliest shooting ever at a US high school, and led Florida's governor to call for the FBI chief to resign.

A person described as someone close to accused gunman Nikolas Cruz, 19, called an FBI tip line on Jan 5, weeks before the shooting at Marjory Stoneman Douglas High School, to report concerns about him, the Federal Bureau of Investigation said in a statement.

"The caller provided information about Cruz's gun ownership, desire to kill people, erratic behavior, and disturbing social media posts, as well as the potential of him conducting a school shooting," it said.

That information should have been forwarded to the FBI's Miami field office for further investigation, but "we have determined that these protocols were not followed," the agency said.

US Attorney General Jeff Sessions said he has ordered a review of FBI procedures following the shooting, carried out by a gunman armed with an AR-15-style assault rifle and numerous ammunition cartridges.

"We have spoken with victims and families, and deeply regret the additional pain this causes all those affected by this horrific tragedy," FBI Director Christopher Wray said in a statement.

The mishandled information followed a tip to the FBI in September about a YouTube comment in which a person named Nikolas Cruz said, "I'm going to be a professional school shooter." The FBI said it investigated that comment but was unable to trace its origins, closing the inquiry until Cruz surfaced in connection with Wednesday's mass shooting.

The FBI's lapse regarding the Jan. 5 tip was met with anger in Florida after US President Donald Trump made remarks seeming to chastise local residents for failing to alert authorities to Cruz's sometimes erratic and violent behavior prior to Wednesday's shooting rampage.

Cruz has been charged with 17 counts of premeditated murder.

Florida Governor Rick Scott said Wray, appointed to head the FBI by Trump last year after the president fired James Comey, should step down over the agency's blunder.

The FBI separately has been criticized by some Republicans over its investigation of issues relating to Russia and the 2016 presidential election.

The massacre has raised concerns about potential lapses in school security and stirred the ongoing US debate pitting proponents of tougher restrictions on firearms against advocates for gun rights, which are protected by the US Constitution's Second Amendment.

Authorities acknowledged that the tips to the FBI were not the only indications that Cruz was troubled.

Broward County Sheriff Scott Israel told a news conference his office had received about 20 "calls for service" in the last few years regarding Cruz and would scrutinize all of them to see if they were handled properly.