Japanese convenience-store chain 7-Eleven has suffered its first year-on-year downturn in more than nine years.

The decline in monthly sales throughout the chain has been attributed to heavy rains and the hack of its doomed 7Pay e-payment platform last month, which prompted customers to use rival services.

Sales chainwide dropped 1.2 per cent last month, with a 5.6-per-cent decline in same-store customer traffic. The inclement weather has also affected sales of particular items such as drinks and ice cream.

7-Eleven’s same-store sales receded 3.4 per cent this month, while the number of franchises grew 2.7 per cent to 20,990 stores.

7-Eleven has discontinued its 7Pay service following a security breach that prompted the firm to stop the app from charging linked cards and put a block on new registrations.

The firm has also been struggling with its 24-hour service model, with some franchisees growing increasingly uncomfortable with rising labour costs involved with round-the-clock opening hours.