Mariona Caldentey's second-half stoppage-time penalty secured Arsenal a dramatic 1-0 win over Danish side HB Køge to open their Champions League campaign at Meadow Park.

There were wholesale changes for Gunners boss Renee Slegers, who inserted eight different faces into her starting line-up from Sunday's 1-1 Women's Super League draw with Manchester United.

Chloe Kelly had the ball in the back of the net in the first half, but the England forward's would-be opener was disallowed following a VAR check.

Arsenal, who had lacked end product throughout, were gifted an opportunity when Selina Cerci was brought down and substitute Caldentey secured all three points with a bottom-corner finish.

Greek referee Eleni Antoniu was called to the monitor after Kelly beat Alberte Vingum in the 12th minute, but it was chalked off after it was determined Stina Blackstenius had been offside in the build-up.

Maanum drew another save in the 25th minute, with the game rarely venturing outside the visitors' half until Macy Schultz's deflected effort drifted towards the crossbar.

There was a cross-shot from Maanum, who could not connect with a teammate, before a Kyra Cooney-Cross effort also drifted wide.

Blackstenius was replaced by Alessia Russo after the break and there were a couple of Arsenal chances in quick succession in what started as a more end-to-end opening to the second half, including a Smilla Holmberg free-kick punched away by Vingum.

The clinical finish, though, still evaded Arsenal, who wasted a handful of set-pieces and watched as Maanum directed an effort over the bar.

Holmberg prevented danger with an alert clearance after Emelia Oskarsdottir's cross fell loose, then came within a couple of inches as her corner caught the crossbar directly.

Then, in the third of four minutes of stoppage time, Yukina Sakabe sent Cerci tumbling. Antoniou pointed to the spot, and Caldentey buried the ball past Vingum.