Roberto Martinez's men were dominant from start to finish in a deserved victory and, while Romelu Lukaku also caught the eye, Mertens was on another level, scoring twice and setting up another two in an eye-catching display in Brussels.

Things looked ominous for Estonia very early on as Belgium cruised into a comfortable 2-0 lead inside 16 minutes thanks to goals from Thomas Meunier and Mertens.

Hazard opened up a three-goal cushion with a fine Mertens-inspired effort, though Henri Anier's goal just before the half-hour mark saw Belgium's defence breached for the first time in qualifying.

There was never any danger of a comeback. though, and Yannick Carrasco netted Belgium's fourth after 62 minutes to round off a brilliant team move, before Ragnar Klavan directed a Mertens cross into his own goal.

The magnificent Mertens added a glorious sixth with 22 minutes to go and Lukaku wrapped things up with a late double as Belgium eased to a maximum 12 points from four matches, leaving them two clear of Greece.

Belgium's preparations were not helped by injuries to Mousa Dembele, Vincent Kompany and Christian Kabasele, but it looked completely unaffected and effectively ended Estonia's hopes inside the first 25 minutes.

Meunier broke the deadlock just eight minutes in, making the most of hesitant goalkeeping from Mihkel Aksalu to head Carrasco's cross in at the back post.

Lukaku almost doubled their lead shortly after when he struck the post, but Belgium did not have to wait much longer for the second – Mertens seeing his fierce 25-yard drive deflect off Klavan and beat Aksalu.

Mertens then turned provider as the host moved 3-0 ahead, with the Napoli star feeding Hazard in behind the defence and the captain producing an emphatic finish.

Anier reduced the arrears on the half-hour mark, turning inside the area and coolly picking out the bottom-left corner from 14 yards.

But the host managed to restore the three-goal advantage and they did so in style just after the hour.

Mertens released Lukaku into the right side of the area and the Everton star's squared pass into the danger zone was left by Eden Hazard for Carrasco to smash in at the far post.

Mertens was integral again just two minutes later as his low cross was diverted past Aksalu by Klavan.

There was no such fortune about Belgium's sixth, though, as Mertens brilliantly chipped Aksalu from just inside the area.

Lukaku then took over in the final 10 minutes, drilling a left-footed effort in after good play by Kevin De Bruyne, before rounding things off with a smart finish into the bottom-right corner after being released by substitute Youri Tielemans.