Mystery lights in the sky over Bermuda were caused by a US Navy missile-firing exercise off the US East Coast -- not little green men from Mars.

And the cause of Saturday night's scare was a test launch at sea of a pair of three-stage rockets designed to carry nuclear warheads from the huge Ohio-class submarine USS West Virginia .

NASA at Cape Canaveral in Florida said they had no launches at the weekend.

But a spokeswoman added: "The US Navy had some operations at sea on Saturday night -- that was probably what people saw.'' US Consul General Robert Farmer said he had been given a briefing by the Pentagon on the light show.

He said: "They do this on a regular basis and particularly when it's done in the evening, you get quite a show.

He added: "If we upset anyone it was inadvertent.'' US Navy sources would not reveal exactly what their ships were up to at the weekend.

But a spokeswoman confirmed two massive Trident 2 D5 missiles -- minus their deadly payload -- were test-fired from the West Virginia off the East Coast of the USA on Saturday night.

Bermuda Police Service and Harbour Radio were flooded with calls after the lights appeared in the sky around 8 p.m.

Eywitnesses described the phenomenon as "two streaks of light'' and "a swirling trail of light''.

One woman said at first it looked like "a helicopter with a searchlight on it'' which "just evaporated.'' A spokesman for Harbour Radio said: "A missile launch would certainly explain the stuff going up into the air -- it's what we expected.'' And the spokesman added one of the Harbour Radio staff, an ex-member of the Royal Navy's civilian support arm, the Royal Fleet Auxiliary, had suggested a rocket as the probable cause of the alarm.

He said: "We had a flood of calls in the space of 15 minutes. I was so busy, I didn't get a look at it myself.'' The sub launch explanation was backed by a Scots chartered accountant, who watched the lights travelling west to south through powerful binoculars from a Paget vantage point.

The man said: "The lights were flame-out from booster rockets -- I watched booster rockets fall off and spiral away.

"It looked like a magnesium burn, it was so bright and there was a lot of condensation.

"There was no noise so it had to be high and with the split, it had to be some kind of rocket launch.'' Trident 2 D5s are carried mostly in the Ohio class fleet -- the US Navy's frontline nuclear deterrent.

The ballistic missiles, also deployed by the Royal Navy, are designed to carry multiple warheads which can be individually targeted.

Trident rockets -- created to strike at the heart of the former Soviet Union from their hard-to-find nuclear submarine platforms -- have a range of around 6,500 nautical miles and power themselves to enormous heights before descending on their designated targets.

MILITARY MIL