Wilmots's fancied side enjoyed plenty of early possession but clear sights of goal were scarce, Axel Witsel having Belgium's only attempt of note in the first 20 minutes with a shot that Raïs M'Bolhi swatted away – they were soon behind to Algeria's first World Cup goal in six matches.

Left-back Jan Vertonghen brought down Feghouli, attempting to get on the end of Faouzi Ghoulam's cross, and the Valencia CF midfielder dusted himself down to send Thibaut Courtois the wrong way from the spot.

Rocked, Belgium responded with Witsel having another long-range effort pushed wide by M'Bolhi. On the one occasion they did unlock the Algeria defence in the first half, Nacer Chadli, after a give-and-go with Eden Hazard, shot straight at the PFC CSKA Sofia keeper.

M'Bolhi's eagerness to intercept Merten's corner five minutes into the second period ended with the ball hitting the unsuspecting Witsel and flying over the crossbar. Frustrated by his team's lack of a cutting edge, Wilmots replaced Romelu Lukaku with LOSC Lille's 19-year-old Divock Origi, who was denied his first international goal by the legs of M'Bolhi.

The pressure told and the equaliser came via the head of Fellaini, who glanced in Kevin De Bruyne's left-wing delivery via the underside of the bar. Ten minutes later Mertens finished off Hazard's incisive pass to ensure Belgium's return to the big time was a winning one.