Greater Brisbane will be locked down from 6pm on Friday in a bid to stave off a possible outbreak of the highly contagious UK variant of COVID-19 after a positive community test on Thursday.

Massive crowds flocked to supermarkets stripping shelves of toiletries, perishables and canned goods with lines stretching for hundreds of metres at some stores.

Police were called in to untangle traffic gridlock around major supermarkets and shopping centres.

Shoppers faced long waits of up to two hours in the hours before the deadline with social media flooded with images of bare shelves and long checkout lines.

Residents in the council areas of Brisbane, Logan, Ipswich, Moreton Bay and Redlands will be required to stay at home until 6pm on Monday.

After encouraging shoppers to "only buy what they need" supermarket giants Woolworths and Coles reintroduced storewide limits to cope with the overwhelming surge in demand.

Shoppers are restricted to purchase limits of two items from a range of toilet paper, anti-bacterial products, and canned, frozen goods from Friday.

"We understand this is an anxious time for Brisbane residents. However, we want to reassure our customers we will remain open as an essential service to support their food and grocery needs during the temporary lockdown," Woolworths Supermarkets Director of Stores Rob Moffat said.

"We have stock to draw on from our suppliers and distribution centres, and it will continue to flow into stores in large volumes.

"We encourage everyone to continue shopping as they usually would and only buy what they need."

Coles Chief Operating Officer Matt Swindells said the health and safety of customers and team members remained Coles' top priority with all staff within the hotspot required to wear masks.

"We have well-established safety protocols based on what we have learned from COVID restrictions implemented in other states," Mr Swindells said.

Greater Brisbane people face the first mandatory order to don face masks outside their homes, prompting a rush to get the essential protection.

Shoppers also have swarmed pharmacies and other outlets where the masks have been sold in bulk in recent months.

Queensland Health has called for calm, reminding the Brisbane community that supermarkets and essential businesses will remain open.

"There are no concerns that supermarket supplies are at risk during this three-day period," a spokesman said.

Greater Brisbane will enter the hard lockdown after a cleaner at a quarantine hotel was diagnosed with the UK variant of COVID-19.

People will only be allowed to leave their home for essential work, exercise, essential shopping, to access healthcare, or to look after the vulnerable.

Masks are mandatory for anyone outside their home, aside from children under 12.

Shoppers have been reminded to adhere to social distancing.

Premier Annastacia Palaszczuk said the state had decided "to go hard and go early" to contain potential spread of the virus.

"If we do not do this now it could end up being a 30-day lockdown," she said.

WHAT ITEMS HAVE PURCHASE LIMITS BEEN IMPOSED ON?

Woolworths has introduced purchase limits of two items on the following products for customers in Greater Brisbane (including the LGA's of Brisbane, Logan, Ipswich, Moreton, and Redlands):

Toilet rolls, paper towels, tissues, liquid soap, anti bacterial wipes, fresh and long life milk, eggs, pasta, noodles, rice, flour, sugar, bread, canned vegetables, canned tomatoes, canned fish, all meat including sausages, burgers and chicken, frozen vegetables, chips, fruit, and desserts.

Australian Associated Press