Belgium moved two points clear at the top of their Nations League group as they came from behind to thump Iceland 5-1.

Roberto Martinez's men fell behind in bizarre fashion through Holmbert Fridjonsson's deflected effort that marked the first of three goals in seven minutes.

Axel Witsel promptly levelled and Michy Batshuayi made it 2-1 to hosts Belgium, who spurned further first-half chances to extend the lead.

But Dries Mertens put Belgium firmly in command early in the second half before Batshuayi doubled his tally and Jeremy Doku bent home a brilliant first senior international goal.

It is a win that gives them breathing room from England in Group A2 after Gareth Southgate's men were held to a goalless draw by Denmark.

The flurry of goals started in remarkable fashion in the 10th minute when Fridjonsson's effort from the edge of the area deflected off Jason Denayer and over the head of a helpless Koen Casteels.

Iceland's lead lasted just three minutes when Witsel's effort crossed the line before being cleared, the Borussia Dortmund man pouncing after Ogmundur Kristinsson tipped Mertens' free-kick onto the crossbar.

And Witsel was heavily involved when the turnaround was completed in the 17th minute as Kristinsson could only parry his low effort as far as Batshuayi, who tucked home from point-blank range.

Belgium then could have put daylight between themselves and the visitors but Mertens fired over the bar.

Kristinsson denied Mertens shortly before half-time but five minutes into the second half, after Kevin De Bruyne's shot narrowly deflected wide, the Napoli forward atoned for his earlier miss.

De Bruyne was typically to the fore as, following the resulting corner, he slid a neat pass into Mertens, who cut inside off his left foot to fire into the bottom-left corner.

Casteels was forced off and replaced by Simon Mignolet following a collision with Jon Fjoluson but that was a minor blemish on a triumph that became more emphatic in the 69th minute.

Witsel was twice denied before De Bruyne played in substitute Yari Verschaeren, whose cutback was flicked home by Batshuayi.

Doku applied the finishing touches, collecting a wonderful pass from De Bruyne before coming in from the left and curling a sublime finish into the top-right corner.

What does it mean? - Red Devils set pulses racing

With De Bruyne, Mertens and Witsel standout performers, Belgium produced a typically scintillating attacking display. They dominated the play - completing 90.4 per cent of their 784 passes - and finished with 20 shots and 11 on target. The margin of victory could have been much greater.

De Bruyne shows his class

De Bruyne delivered yet another demonstration of his PFA Footballer of the Year quality with an instrumental showing that saw him produce three key passes including assists for Mertens and Doku.

Hermannsson's horror show

Plenty of Iceland players endured evenings to forget, but right-back Hjortur Hermannsson will be particularly keen to put this one behind him as Belgium found joy down the left time and again. 

Hermannsson completed just 59.1 per cent of his passes, won only a third of his 12 duels and conceded two fouls, including one that led to Belgium's opener.

What's next?

These two sides will play the return fixture in Iceland on October 14. Before that, however, Belgium have a friendly with New Zealand and a trip to Wembley to face to England.

Of much larger importance to Iceland will be their Euro 2020 play-off with Romania on October 8. They then return to Nations League action against Denmark before welcoming Belgium to Reykjavik.