Wahbi Khazri found a second consolation for the Tunisians after steering home a cross-field pass a minute from time.
"So, when you have to change that many players, you put more pressure on your defenders but I think the Belgium team deserved to win".
Belgium will need to keep up their performances in a steady manner, if they need to reach the last 16 and that too achieve a splendid win over. Belgium then claimed a 1-0 victory in a friendly in June 2014.
Any faint hopes that Tunisia had of clawing their way back into the game were extinguished six minutes into the second half when Hazard scored his second.
The game at the Spartak Stadium here was billed as a test of credentials for Belgium against a Tunisia side who had showed they were an awkward, stubborn team to beat in their opening match against England.
Belgium moved to the brink of the World Cup knockout rounds on Saturday.
Any thoughts that the rampant Belgians would accelerate out of sight were dispelled - at least briefly - just two minutes later, though.
Eden Hazard fired the ball to the net and Belgium gained their 4th goal of the game and leads by 3 goals.
While Hazard entertained with his box of tricks and surging runs, Lukaku arguably was the headline act with his ruthless finishing.
Tunisia are a lot more upbeat now, a few days on from their late defeat to England. On Sunday, a draw for England against Panama would knock the African team out of the World Cup.
Where is FIFA World Cup 2018 Belgium vs Tunisia match being played?
Vardy was an unused substitute in the 2-1 win over Tunisia and faces one of the toughest battles for game time given he is effectively challenging for the same position as captain Harry Kane.
The FIFA World Cup 2018 Belgium vs Tunisia match will be broadcast live on Sony ESPN/HD, Sony TEN 2/HD and Sony TEN 3/HD.
SI TV is also now available on fuboTV.