DUBAI, June 20 (Reuters) - Over 150 fridges stocked with free food for those in need have become a city-wide phenomenon in Dubai after a lone activist started with a single unit during last year's holy month of Ramadan.

The Ramadan Sharing Fridge initiative was the brainchild of Australian Sumayyah Sayed, who left the first fridge outside her house and stocked it with food and drinks for the city's poor.

Around 25,000 ordinary members of the public have donated to the scheme, helping to boost the numbers of fridges this year, with approximately 400 people making use of the service each day at one fridge that Reuters visited, organisers said.

"Every day we have 10 to 15 donors who come individually on their own and they give us some dry items, Labans (milk), they give us biscuits, fruits and juices. So we make packs of these individually and we hand it over," fridge manager Swathi Santhosh told Reuters.

The fridges around the city are marked on a digital map and promoted on social media channels. They are located everywhere from car parks, to construction sites to private residences. They are mostly concentrated in the downtown area of the city.

A queue of construction workers were seen at one location that Reuters visited.

Those in charge of distributing food from the fridges are volunteers, dressed in regular street clothes and without affiliation to any organisation.

During Ramadan, the ninth month of the Islamic calendar, observant Muslims fast from dawn to dusk - refraining from consuming food and drinking liquids.

(Reporting by Tarek Fahmy, writing by Mark Hanrahan and Babatunde Ayoadein in London, editing by Pritha Sarkar) ((Mark.Hanrahan@thomsonreuters.com;))