Hazard scored with a sixth-minute penalty kick he earned by being tripped, and Lukaku angled a low, left-foot shot into the corner of the opposing goal.
"Give huge credit to Tunisia, they wanted to win from the beginning, they pressed high up, they were happy to leave space and the credit we deserve is that we used that space well".
"Romelu will try to score as many goals as he can but not at all costs", he said. After a neat triangle in the middle of the park sucked in the Tunisian defence, Toby Alderweireld lifted an inch flawless through ball to Hazard, who rounded Ben Mustapha before finishing calmly into an open net.
And Hazard got his fourth by leaving the goalkeeper in the dust.
Michy Batshuayi should have made it 5-1 for the Red Devils 11 minutes before time with a glorious chance inside the box but his strike hit the underside of the crossbar.
Tunisia captain Wahbi Khazri got his team's second with nearly the last kick of the match.
Belgium opened with a 3-0 win over Panama 3-0 and another win against Tunisia would nearly certainly secure a place in the knockout stages from Group G. Video review confirmed the trip was on the white line of the penalty area, not outside as Tunisia claimed.
And there was a moment in the first-half from Lukaku that really got fans talking, with the likes of Piers Morgan and rugby referee Nigel Owens all praising the Belgian striker. Bronn and Ben Youssef were both replaced after leaving the field on stretchers.
Martinez also dismissed suggestions winning Group G may not be beneficial due to the raft of surprise results elsewhere.
Ahead of next Thursday's likely top-spot shootout with England in Kaliningrad, however, Martinez has confirmed that Hazard, Lukaku and fellow forward Dries Mertens - each substituted against Tunisia - are all carrying knocks that could rule them out.