Belgium manager Roberto Martinez has insisted that "many things can be better" for his side, despite thrashing Tunisia 5-2 to make it two wins from two at the World Cup.

The Red Devils have now netted eight goals in their opening couple of Group G outings, having also brushed aside Panama 3-0 at the start of the week.

Martinez was particularly pleased with the clinical finishing on show from striker Romelu Lukaku, who doubled his tally for the tournament to four goals, but the Spaniard is adamant that there is more to come against England next Thursday.

"[Lukaku] will try to score as many goals as he can but not at all costs," he told reporters after the match. "I thought he was incisive, in the right position, in a confident mood, in front of goal he was as clinical as you might expect.

"Many things can be better. This was a game that suited our style, you have to give credit to Tunisia. They wanted to win from the beginning, press high up.

"The credit that we deserve is that we took those opportunities well. We are still growing. With a two-goal lead we should have controlled the game a little bit better."

Belgium sit at the top of the Group G standings, three points ahead of England who face Panama in their game in hand on Sunday.