Belgium coach Marc Wilmots warned any opponents who opened up against his team would be punished after their 1-0 win against Sweden on Wednesday.
Wilmots was heavily criticised after Belgium, boasting several Premier League stars, began with a 2-0 defeat to Italy, but his side have bounced back to beat Republic of Ireland and Sweden.
The win, thanks to Radja Nainggolan's late strike, earned Belgium a place in the last 16, where they will face Hungary.
"They were obliged to open up and if you do that against us you will be punished," said Wilmots. "Six points from nine is very good and since the defeat by Italy we have got better, we've kept two clean sheets in a row."
"People thought we were dead after the first game but we are back on track and we have come through a very difficult group," added Wilmots whose side finished second in Group E, behind Italy.
But Belgium's players were more cautious than their coach.
"Hungary will be tough. We saw the last minutes of their game against Portugal," said Eden Hazard. "They give 200 per cent and have very good players. We need another good performance to qualify for the quarter-finals."
Goalkeeper Thibaut Courtois agreed that Hungary, initially seen as outsiders to reach the knockouts, would be hard work.
"The last 16 is really open. But they're all difficult countries to beat. We cannot think that it will be an easy match," he said.