US fast food company Burger King has posted its best quarterly sales increase in nearly a decade.

The company says the sales boost is the result of a promotional ‘two for $5’ campaign, the introduction of the new spicy BLT Whopper and a boost in breakfast sales – no single “silver bullet”.

Burger King’s same store sales rose 6.9 per cent in the US and Canada, according to parent Restaurant Brands International, but it declined to say if it was the result of increased customer traffic or a high per customer spend. Given the low cost promotional offer, it’s likely to have come at the cost of margins.

Burger King’s performance is all the more significant due to its coincidence with a 2.6 per cent fall in sales by its larger rival McDonald’s.

Global same store sales rose 4.6 per cent at Burger King.