"There's a giant lizard on the track," exclaimed Red Bull driver Max Verstappen.
"You came face to face with Godzilla," the 18-year-old's engineer told him over the pit-to-car radio after the startled Dutchman alerted the team to the reptile's presence.
The incident triggered a Twitter flurry and plenty of amusement.
"New friend in FP3," commented McLaren driver Fernando Alonso on Instagram to accompany a picture of the animal on the asphalt.
Drivers are used to groundhogs and foxes making track incursions at Canada's Gilles Villeneuve circuit in Montreal while stray dogs proved a danger when the sport raced at India's Buddh circuit near New Delhi.
Deer have appeared on track in Austria in the past, snakes in Malaysia and a cat ran out in front of cars in Azerbaijan's debut race this year in Baku.
There have also been a number of human incursions, including one at last year's Singapore race when a lone intruder ambled across the floodlit track midway through the race and then strolled by the metal fences as cars came past.
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"I had to look again as I wasn't sure if I had a problem with my eyesight and that I actually saw somebody crossing the track," Ferrari's race winner Sebastian Vettel told reporters at the time.