Marco Reus marked his first appearance of the season with a hat-trick as Borussia Dortmund consolidated top spot in Group F with an 8-4 victory over Legia Warsaw, breaking a Champions League record in the process.

Germany forward Reus, who missed out on Dortmund's Der Klassiker triumph over Bayern Munich last time out with a heel injury, had not featured for Thomas Tuchel's side since May prior to Tuesday's clash at Signal Iduna Park.

And he wasted no time in returning to goal scoring form as he sealed his hat-trick in second-half stoppage time.

It was Legia who took the lead through Aleksandar Prijovic early on, but Shinji Kagawa's double and Nuri Sahin's header put Dortmund well in control.

Ousmane Dembele added Dortmund's fourth after Prijovic had snatched another for Jacek Magiera's side, with a Reus double coming before Michal Kucharczyk pulled another one back for Legia.

Felix Passlack's header made it seven for Dortmund, before Nemanja Nikolic netted Legia's fourth - Reus on hand to set a new Champions League record of 12 goals in one match.

Despite their lowly position in the group, Legia - who drew 3-3 with Real Madrid on matchday four - started brightly and were rewarded when Vadis Odjidja-Ofoe took advantage of some nonchalant Dortmund defending to tee up Prijovic, who proceeded to curl in a wonderful finish off the outside of his boot.

However, the hosts swiftly restored parity, Kagawa ghosting in behind Legia's static back-line to head home Dembele's cross 17 minutes in.

Matters got worse for Legia straight from the restart, as Dembele and Kagawa again combined on the edge of the box, the latter thumping a venomous finish past Radoslaw Cierzniak.

Legia's stand-in goalkeeper was at fault as Dortmund got their third in as many minutes, inexplicably parrying Reus' free-kick onto the head of Sahin.

More shambolic defending from Dortmund allowed Prijovic to double his tally with a neat strike, but the forward could only find the woodwork from point-blank range soon after and Legia were made to pay from the resulting counter.

Ciezniak was unable to keep out Dembele's powerful effort from the edge of the area, with Reus getting in on the act three minutes later when he steered in Kagawa's cross.

Weidenfeller finally made a save when he held onto Kucharczyk's header, before Kagawa had a goal disallowed for offside at the culmination of an incredible first-half.

Dortmund netted six in the reverse fixture on matchday one, and Tuchel's side matched that feat on 52 minutes, Reus turning home another tap-in after latching onto Dembele's pass.

Tuchel's side continued to concede space at the back, though, and were duly punished when Kucharczyk raced in behind and prodded a tidy finish over Weidenfeller.

Substitute Pierre-Emerick Aubameyang struck the upright shortly after his introduction, though Passlack did add a seventh for the hosts when he nodded in the rebound from Andre Schurrle's shot, only for Nikolic to net from the restart.

But the record was broken when, in the final minute of added time, Reus completed his hat-trick, maintaining Dortmund's two-point lead at the top of Group F.