Atalanta put in a magnificent performance to crush Midtjylland 4-0 in Denmark, with Duvan Zapata, Papu Gomez, Luis Muriel and Aleksei Miranchuk on target.
Liverpool won 1-0 away to Ajax, so the Bergamo Boys are top of the group on goal difference.
La Dea dived into their second Champions League campaign and visited Danish debutants Midtjylland, in a group that also has Liverpool and Ajax. They were missing Ruslan Malinovskyi, Mattia Caldara, Pierluigi Gollini and Cristiano Piccini, while Luis Muriel was preferred to Josip Ilicic in heavy rain.
Robin Gosens lashed an angled drive across the face of goal and Pione Sisto blasted over from distance, but Muriel’s viciously dipping free kick tested the goalkeeper.
Duvan Zapata rattled the woodwork on 16 minutes, smacking the near post from a tight angle after a quick Remo Freuler through ball.
The Colombian forced Jesper Hansen into a fingertip save and eventually broke the deadlock when Cristian Romero knocked down Rafael Toloi’s cross following a set play for Duvan Zapata to finish off from close range.
Marco Sportiello had to make his first save of the match on Anders Dreyer’s daisy-cutter, pushing it round the base of the upright following a great run from Jens-Lys Cajuste.
However, La Dea doubled their lead with a moment of magic from Papu Gomez, who gathered from Duvan Zapata and unleashed an unstoppable rocket from 20 metres out, clipping the underside of the bar to give Hansen no chance.
Duvan Zapata was involved again, his snapshot only parried by Hansen into the path of Muriel for 3-0.
There was almost a fourth before half-time, Remo Freuler pouncing on a poor back-pass only to fire wide of an open goal.
Gomez had penalty appeals waved away for a Mabil shove, while Sviatchenko’s header and a Mario Pasalic run forced saves, then substitute Josip Ilicic was sent clear on goal only for Hansen to get just enough to push it on to the woodwork.
There was still time for a fourth, as Aleksei Miranchuk came off the bench and curled a stunning finish into the far top corner.
Midtjylland 0-4 Atalanta
Duvan Zapata 26 (A), Gomez 36 (A), Muriel 42 (A), Miranchuk 89 (A)
Midtjylland: J Hansen; J Andersson, Sviatchenko, Scholz, Paulinho; Cajuste (Madsen 76), Onyeka (Kraev 87), Dreyer, Sisto (Anderson 87), Mabil (Vibe 75); Kaba (Evander 60)
Atalanta: Sportiello; Toloi, Romero (Palomino 86), Djimsiti; Hateboer, De Roon, Freuler, Gosens; Gomez (Pasalic 68); Muriel (Ilicic 68), Duvan Zapata (Pessina 80)
Ref: Artur Dias (POR)