Panic buyers have cleared supermarket shelves of bottled water.
Tinned vegetables and toilet rolls are also running low as desperate shoppers stock up amid fears of biological or chemical terrorist attacks.
The items are on a list of recommended goods drawn up by the Home Office in case Britain comes under terrorist attack.
Although there is no specific terrorist threat, Home Office officials have said it is prudent to be prepared.
In Eastbourne, bosses at Asda at the Crumbles noted increased sales in the items on the list.
General store manager James McGovern said today: "The most popular item has been long-life milk.
"But we've seen increased sales of tinned veg and bottled water as well, both items being recommended by the Home Office.
"I think there is a small element of fear creeping into the minds of shoppers. It looks as though they are being cautious."
Supplies of water were also low at Sainsbury's in The Drove, Newhaven.
The store was forced to put a new delivery of canned vegetables and bottled water on to the shelves as soon as it arrived last night, instead of waiting until this morning as usual.
Manager Jim Mullin said: "There were 8ft gaps in the shelves where the multi-packs of water once stood.
"People who perhaps would usually only buy one bottle have been buying packs of 12.
"There is no doubt people are panic buying. We have been told to expect bigger deliveries in the next few days."
At Eastbourne's two Sainsbury's stores, in the Arndale Centre and Hampden Park, bosses have seen similar patterns.
Arndale duty manager Paul Stonham said today: "Like other stores, sales have increased in long-life milk, tinned goods and bottled water.
"One day last week our shelves were completely stripped of bottled water.
"Other stores have been similarly hit in the same areas."
In Hastings and St Leonards, bosses at Sainsbury's in John Macadam Way, Tesco in Hollington and Safeway in the town centre reported similar trends.
Asda's Brighton stores at the marina and in Hollingbury had sold out of water last night as had Tesco in Lewes.
Other stores were expecting extra deliveries to prevent stocks drying up.
Last night, Nick King customer services manager at Asda Hollingbury, said: "We've been very busy and are completely out of water.
"Some people are definitely panic buying."
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