NEW: Britain has urged households to stock up on enough water, non-perishable food and medicine to be self-sufficient for three days, launching a new "Be Prepared" preparedness campaign.

NEW: Britain has urged households to stock up on enough water, non-perishable food and medicine to be self-sufficient for three days, launching a new "Be Prepared" preparedness campaign.

The government directive recommends about three liters of drinking water per person per day, food that does not need refrigeration or cooking, essential medicines, a first aid kit, a torch, a battery or a winding radio, a charged power bank and cash.

Officials cited severe storms, wildfires, cyber attacks and supply chain disruptions as the main risks, with Defense Secretary Wes Streeting pointing to "increasingly sophisticated cyber attacks" and scenarios such as supermarket checkout systems going down.

Germany followed suit long ago, recommending that households have a 10-day emergency supply, including about two liters of liquid per person per day.