Residents in Bootle, Anfield and Kirkby reported the bizarre activity on social media – with some saying they could be flying saucers.
Matthew Worthington, from Bootle, wrote on Facebook: "Definitely UFOs – the way they're moving just screams aliens."
And Twitter user Sarah Louise joked: "If Liverpool gets invaded by aliens does that mean works cancelled tomorrow?"
Amazingly, another two UFOs were sighted in Birmingham within 48 hours of the Liverpool sighting.