In the most recent update on the ‘International Incident Bulletin’ on its website, posted yesterday (12 January), the postal operator stated: “We are temporarily unable to despatch items to overseas destinations.

“In order to prevent a build-up of export items in our network and support a faster recovery when we restore service, Royal Mail is continuing to ask customers not to post international export items until further notice.

“Items that have already been despatched may be subject to delays. We would like to sincerely apologise to impacted customers for any disruption this incident is causing.

“Our import operations continue to perform a full service, with some minor delays. Parcelforce Worldwide export services are still operating to all international destinations though customers should expect minor delays. Royal Mail’s UK services are still operational.

“Our teams are continuing to work around the clock to resolve this disruption and we will update you as soon as we have more information. An investigation into the incident is ongoing and we are working with external experts. We have reported the incident to our regulators and the relevant security authorities.”

Royal Mail has not commented on the cause of the incident, although according to one of the BBC’s sources, it was caused by “ransomware linked to Russian criminals” called Lockbit.

The BBC said it had seen a ransom note sent to Royal Mail which stated: “Your data are stolen and encrypted.”

A Royal Mail spokesperson did not comment on the nature of the attack to the BBC, but said “there is no end in sight” to the delivery disruption. They also warned of “minor delays” to post coming into the UK, but said domestic deliveries were unaffected.

The incident is causing further disruption for those reliant on Royal Mail’s services, following months of strikes involving over 115,000 postal workers across the Royal Mail network.