Verstappen and Ricciardo traded turns at the top of the timesheet as conditions improved until the former banged in a lap of 1m 48.962s on intermediate tyres towards the end of the session to go 0.7s clear of his team mate.
No one else could get near that - indeed only two men got within two seconds, with Fernando Alonso chief of them for McLaren.
Ferrari's Kimi Raikkonen just failed to edge the Spaniard with a late improvement to fourth on 1m 50.734s, the Finn finishing just ahead of championship protagonists Sebastian Vettel and Lewis Hamilton.
Hamilton, the current points leader, did few laps after an early run, but came out towards the end to improve to 1m 51.517s, which was around half a second quicker than his Mercedes team mate Valtteri Bottas in seventh.
Lance Stroll gave another demonstration of his prowess in the wet as he finished eighth for Williams, just ahead of another impressive youngster – Pierre Gasly, who is making his F1 race weekend debut for Toro Rosso.
The Frenchman, competing in the next races as a replacement for Daniil Kvyat, was comfortably quicker than Toro Rosso’s other debutant, Sean Gelael, who nevertheless finished a creditable P14, and likewise didn’t put a foot wrong.
Renault’s Sergey Sirotkin – another FP1 stand-in – completed the top ten as he outpaced the other yellow car of Jolyon Palmer by a tenth of a second, despite being one of several drivers to spin on the wet track.
Standing in for Marcus Ericsson, Charles Leclerc was 16th on 1m 55.280s to head Sauber team mate Pascal Wehrlein; the German having been another to spin.
The timesheet was rounded out by the Haas’s of Romain Grosjean and Antonio Giovinazzi (who was sitting in for Kevin Magnussen) and the Williams of Felipe Massa, who was the only driver not to record a time after a suspected hydraulic issue.
With rain forecast over the rest of the weekend, it will be interesting to see if Red Bull remain the team to beat.
WATCH: FP1 summary
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