* Find on similar scale to UK, South Sudan oil reserves
* Oil of DRCongo says oil can boost GDP by 25 pct
* Campaigners say Gertler has made huge profits in Congo (Adds industry comment, further explanation in paragraph 3)
By Peter Jones
KINSHASA, Aug 7 An oil company owned by Israeli billionaire Dan Gertler said on Thursday it had discovered around 3 billion barrels of oil in the Democratic Republic of Congo, an amount similar to the proven reserves of oil producers Britain and South Sudan.
The crude was discovered around Lake Albert on Congo's eastern border with Uganda, Oil of DRCongo said in a statement.
An analysis of seismic survey data "indicates around 3 billion barrels of oil in place", it said, although it was not yet clear what portion was recoverable.
"These are very positive results from our extensive seismic campaign," said Giuseppe Ciccarelli, Oil of DRCongo's CEO. "We continue to believe the project has the potential to provide significant revenues and multiple other benefits to the people of (Congo)."
The nearby Ugandan blocks are estimated to hold a similar amount of oil and are being developed by British company Tullow , France's Total and China National Offshore Oil Corp (CNOOC).
Oil of DRCongo said it now plans to prepare for the drilling of two exploration wells on the site by building infrastructure and relocating local communities.
Resource-rich Congo produces just 25,000 barrels of oil per day from onshore and offshore fields in western coastal areas and is seeking to increase production dramatically to boost growth and relieve poverty.
Oil made up just 1.7 percent of Congo's gross domestic product in 2012, according to the International Monetary Fund. Oil of DRCongo said production of 50,000 barrels per day at Lake Albert would expand Congo's economy by 25 percent.
But industry sources say the volumes should be considered provisional and point to the difficulty of exporting the oil from eastern Congo - a region hundreds of kilometres from export points on the shores of the Indian and Atlantic oceans.
"Seismic estimates still need to be confirmed by a serious drilling campaign and I would not be surprised if the amount is reduced by a significant percentage," said one source with experience assessing oil exploration projects in Africa.
Risk consultancy Maplecroft's Ben Payton said oil could, in theory, be exported via a planned pipeline from Uganda to the ocean but added tension between Uganda and Congo made this unlikely.
Oil of DRCongo operates blocks one and two at Lake Albert on behalf of Foxwhelp and Caprikat, both subsidiaries of Gertler's Netherlands-based company Fleurette which has several interests in Congo's mining sector.
Campaign groups such as Global Witness say Gertler, an influential figure in Congo with close ties to President Joseph Kabila's government, received concessions at low prices before selling them on for large profits, particularly in a series of mining deals between 2010 and 2012.
In January, Reuters revealed that Gertler had sold one of his Congo-based oil companies, Nessergy Ltd, to the government for $150 million - 300 times the amount paid for the oil rights.
Gertler, who has joint Israeli and Congolese citizenship and says his firm has invested more than $7 billion in the local economy, vigorously denies receiving favourable deals at knockdown prices.
A spokesman said at the time that the Nessergy rights had dramatically increased in value since they were obtained in 2006, partly due to the discovery of significant nearby oilfields. (Reporting by Peter Jones; Writing and additional reporting by Emma Farge; Editing by David Evans)