* Citi, Deutsche, UBS to auction leftover shares
* Santos shares under pressure from weak oil price (Updates with retail take-up, Santos comment)
MELBOURNE, Dec 2 (Reuters) - Santos Ltd STO.AX retail investors took up 57 percent of their entitlements in a A$1.35 billion ($987 million) share offer, the oil and gas producer said on Wednesday, better than the one-third uptake some media reports had flagged as energy prices remain weak.
The sale to retail investors was part of a A$2.5 billion entitlement offer announced in November after Santos snubbed a takeover proposal and sold some assets to cut debt and prepare for a prolonged period of weak oil prices.
The offer was fully underwritten by Citi C.N , Deutsche Bank DBKGn.DE and UBS UBSG.VX , who will put the remaining shares up for auction, due to be completed before the market opens on Thursday.
Institutions last month took up 86 percent of their entitlements in the earlier leg of the offer which raised A$1.17 billion. The unsold shares from that offer were sold off at A$4.60 a share, a premium to the entitlement offer price of A$3.85.
"The results of the...offer demonstrate recognition from shareholders of the long-term value in Santos and their support for the initiatives the company has taken to substantially strengthen its balance sheet," Executive Chairman Peter Coates said in a statement.
The Australian Financial Review newspaper had said there had been talk the underwriters were left holding between A$900 million and A$1 billion worth of shares in the retail offer.
The A$3.85 offer price was pitched at a massive 35 percent discount to Santos' closing price before it was announced.
Santos shares last traded at A$4.06, down 43 percent this year and well below the A$6.88 a share offered by its jilted suitor Scepter, a fund backed by Brunei and United Arab Emirates royals. ($1 = 1.3678 Australian dollars)