Bright lights in the skies have baffled police and air-traffic controllers.
The unidentified flying objects have been likened to similar strange orange glows seen over Liverpool and Essex.
Witnesses said thousands of people may have seen the bizarre floating orbs.
Air-traffic controllers at Shoreham Airport and Brighton police said they had received inquiries about the UFOs, with as many as eight seen in the sky at one time.
James Gordon-Johnson, of Preston Park Avenue, Brighton, said he was leaving a restaurant in Shoreham with his brother at 11.30pm on November 18 when he saw "what appeared to be a very big orange
light in the sky".
He added: "It was very, very bright but static - it wasn't rising or falling. Another one then appeared in mid-air. Then another.
"It must have been somewhere over Hove Lagoon but the lights were so bright thousands of people must have seen them.
"The next morning I got a phone call from a friend of mine who saw the exact same thing."
Mark Sztopel, from Brighton, told The Argus he saw seven lights moving slowly in an easterly direction across the city at midnight.
He added: "I'm a big plane enthusiast so I know what the lights and characteristics of a plane look like at night, and I can tell you now that these definitely weren't planes."
A spokeswoman for Shoreham Airport said staff had received emails from people inquiring about the glowing objects.
She said: "We closed at 7pm so there was nothing happening here. We've no idea what they could have been."
Police said they also received a report from a man in Hove who said he saw "approximately eight planes coming in over the sea, with no flashing navigation lights, towards Gatwick, in a dead
Officers contacted air traffic controllers at Gatwick who said they knew of no movement in the area.
Sue Heard, a police spokeswoman, said: "We were called out and made checks to establish it wasn't a known aircraft.
"It certainly seems pretty baffling on the face of it but there was a meteor shower on Saturday so maybe the two are connected."
A cloud of comet dust produced a Leonids meteor shower over the weekend, which managers of Herstmonceux Observatory said peaked on Saturday night with a display of shooting stars.
UFO spotters have also linked the orange lights to sightings in Liverpool and Essex, recently revealed as hoaxes created using open flames suspended under plastic bags to produce mini hot-air
But Mr Gordon-Johnson, 33, said: "These weren't meteors - there's no way they were meteors. They were far too big and bright and low in the atmosphere.
"They looked like they were about 3,000 or 4,000ft up. As I kept looking at them they just sat there. I was trying to think of explanations but couldn't think of one.
"It was very odd. If it was just a balloon you wouldn't have seen another just appear at the same altitude. There was no sound. Nothing at all."
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