Japan is facing a shortage of Asahi products, including beer and bottled tea, as the drinks giant grapples with the impact of a major cyber-attack that has affected its operations in the country.

Most of the Asahi Group's factories in Japan have been at a standstill since Monday, after the attack hit its ordering and delivering systems.

Major Japanese retailers, including 7-Eleven and FamilyMart, have now warned customers to expect shortages of Asahi products.

In a statement on Friday, Asahi said it was unable to provide a clear timeline for recovery but had started partial manual processing of orders and shipments.

Asahi is the biggest brewer in Japan, but it also makes soft drinks and food products, as well as supplying own-brand goods to other retailers.

It owns Fullers in the UK and global brands including Peroni, Pilsner Urquell and Grolsch. However, Asahi has said that only its operations in Japan - which account for about half its sales - have been affected by the attack.

In its latest statement, Asahi said that as a result of containment measures following the attack, ordering and shipment systems in Japan had been affected and it was also unable to receive emails from external sources.

Asahi also said it was preparing to reopen its call centre operations next week.

Atsushi Katsuki, Asahi president and group chief executive, apologised for the disruption, stating, We are making every effort to restore the system as quickly as possible, while implementing alternative measures to ensure continued product supply to our customers.

In a statement on Thursday, FamilyMart - which is one of Japan's largest convenience stores - said its Famimaru range of bottled teas, which are made by Asahi, were expected to be in short supply or out of stock.

We sincerely apologise to our customers for any inconvenience caused, said FamilyMart, adding that it was working with Asahi to resume the sale of the products.

7-Eleven has halted shipments in the country of Asahi products, including its popular Super Dry beer, indicating a shortage for customers. Lawson, another major retail chain, also anticipates a short supply of Asahi products starting Friday, while Life Cooperation has cautioned that Asahi products may soon go out of stock.