LOS ANGELES - THREE people were killed and two others missing after a US F/A-18 fighter jet slammed into a densely populated residential neighbourhood in California on Monday, officials said.

The accident occurred shortly before midday (4am Singapore time) when the two-seater plane spiraled out of control and crashed into two homes in the University City suburb of San Diego, officials said.

The pilot of the aircraft, which had been taking part in a training exercise and was approaching the Marine Corps Air Station in Miramar when it crashed, ejected safely and landed in the grounds of a nearby school.

Plumes of thick white smoke billowed from the crash site, where dozens of firefighters battled to extinguish flames amid the charred wreckage of two homes in the leafy neighborhood.

The two fatalities were confirmed at a mid-afternoon press conference attended by San Diego Mayor Jerry Sanders, police, fire and military officials.

'Our hearts go out to the victims,' Mr Sanders told reporters.

The bodies of the victims were found in the scorched rubble of the crash site. Two other people were still missing, officials said.

The exact cause of the accident was not known but Steve Diamond, a former military pilot who witnessed the crash, said the downed flier told him the plane suffered a mechanical problem.

The pilot was flying quite low in the moments before he ejected, Diamond said. 'Other than that, there was no overt indication of any kind of catastrophic failure,' he added.

The pilot appeared to be unhurt, he added. 'Turns out that after he extracted himself from the tree, he was OK. He was in good shape.'

Another eyewitness told a local television reporter that the plane had spiralled out of control like a scene from 1986 movie 'Top Gun,' the hit film about a US Navy fighter pilot played by Tom Cruise.

'It just spiralled right out of 'Top Gun'. It came flying down. My mother screamed,' the man said, reporting that he had seen the plane's pilot after he landed in a tree at a nearby school playing field.

'He just looked like he was dazed like 'Oh, my God, what happened over civilian air space?',' he said.

Ms Pia Mantovani-Sud told the San Diego Tribune she had been inside her house on the street where the plane crashed when she heard the jet crash.

'I heard a boom boom boom ... I came out and saw my neighbour's house on fire,' she told the paper's website.

Resident Nora Bhes added: 'It sounded like a thunderstorm with a real screech at the end of it.' -- AFP