Panama, competing at the first World Cup in their country’s history, had fought bravely to keep the game goalless during the first period, despite long periods of possession for Lukaku and his colleagues, but, after the break, the floodgates opened and the Europeans made their domination count.
The result took Belgium top of Group G, ahead of England’s match against Tunisia in Volgograd on Monday evening.
Lukaku’s club colleague, Marouane Fellaini, was an unused substitute for Roberto Martinez’s men, but the United midfielder could feature on Saturday when Belgium continue their campaign against Tunisia in Moscow.