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* Atlas Mara buys UBN stake for $270 million
* Brings total stake to 29.9 percent
* UBN formerly owned by Barclays (Adds company confirmation, comments from management)
By Chijioke Ohuocha and Steve Slater
LAGOS/LONDON, Sept 5 (Reuters) - Atlas Mara, theAfrican investment vehicle of former Barclays boss Bob Diamond,said it had increased its stake in Union Bank of Nigeria to almost 30 percent for $270 million.
The deal marks the third significant acquisition by AtlasMara, set up last year by Diamond and Africa-based entrepreneurAshish Thakkar, as it seeks to build the firm into Africa'sleading bank. It raised $300 million last month to add to itsacquisition war chest.
Atlas Mara said on Friday it was buying the additional 20.9percent stake from Asset Management Corporation of Nigeria(Amcon). Reuters reported on Thursday Atlas Mara was in talks tobuy the UBN stake.
UBN has 340 branches across Nigeria and had about $6.3billion of assets, $3.1 billion in deposits and $1.3 billion inequity at the end of June. Atlas Mara said it purchased thestake at about book value.
UBN was established as Colonial Bank in 1917, and from 1925until the 1970s was owned by Barclays, the British bankthat Diamond led before being ousted under a cloud two yearsago. UBN's market capitalisation is about $850 million.
"This is a very significant acquisition ... we will have asignificant stake in a key Nigerian bank and we will also haveestablished strategic market positions in three of Africa'sleading economic communities: the Southern Africa DevelopmentCommunity, the East Africa Community and Economic Community ofWest African States," Diamond said in a statement.
Previous deals have given Atlas Mara a platform in severalcountries including Botswana, Mozambique and Tanzania.
It said in a prospectus published last month it wasconsidering buying a minority stake in a bank in Nigeria, whichis sub-Saharan Africa's largest economy and one of its mostattractive and fast-growing markets for banking.
Diamond is one of the world's best-known bankers afterspearheading the growth of Barclays' investment bank beforebeing forced from his job as CEO in 2012 by UK regulators afterthe bank was fined for attempted rigging of Libor interestrates.
His plans in Africa could put him in direct competition withBarclays, which has had a presence there since the 1920s and isone of the biggest international banks on the continent.
UBN was known as Barclays Bank CDO (Dominion, Colonial andOverseas) when it was bought by Barclays, and became BarclaysBank of Nigeria in 1969 after Nigeria's independence, accordingto the bank's website.($1 = 0.6128 British Pounds) (Additional reporting by Clare Hutchison; Editing by KeironHenderson and Susan Thomas)
