Marco Reus and Shinji Kagawa gave Borussia Dortmund a routine 2-0 win over Mainz in a game overshadowed by tragedy at Signal Iduna Park.

Much of Sunday's Bundesliga match was played out in front of a subdued crowd after reports filtered through that two supporters had suffered heart attacks in the stands.

Dortmund confirmed shortly after full-time that one spectator had passed away, while the other is stable after being taken to hospital. The club added: "There are more important things than football. #RIP"

On the pitch, goals either side of half-time from Reus and Kagawa sealed a victory that moves Dortmund back to within five points of Bundesliga leaders Bayern Munich.

Dortmund were on top from first whistle to last, with Mainz goalkeeper Loris Karius called into action to deny Pierre-Emerick Aubameyang and Henrikh Mkhitaryan among others, but their win pales into insignificance when considered along with events off the pitch.

Marcel Schmelzer got a chance to break the deadlock midway through the first half after cutting inside from the left and dancing past two opponents, but Karius did well to keep out the full-back's right-footed shot.  

Gonzalo Castro prevented Mainz from taking a surprise lead shortly after when he cleared Stefan Bell's low shot off the goalline, with Dortmund goalkeeper Roman Burki already beaten.  

But Reus was on hand to put Dortmund ahead on the half-hour mark, as he coolly slotted his 10th Bundesliga goal of the season beyond Karius after latching onto Castro's clever throughball.

Karius then did well to rush off his line and gather before Mkhitaryan could tap home Schmelzer's low cross from the left, preventing a second Dortmund goal shortly after Reus' opener.

Mainz's keeper again showed his class early in the second half when he denied Kagawa from close range, blocking the Japan international's toe-poke from five yards out with his legs.

Aubameyang was next to be frustrated by Karius in the 51st minute, with Dortmund's top scorer denied twice in the space of 30 seconds.

Reus tried his luck from a difficult angle at the hour mark, before Mkhitaryan blazed over.

Reus then wasted a gilt-edged chance after being set up by Mkhitaryan, before Kagawa eventually sealed a hollow win, tapping home from close range after some good work from Aubameyang.