* Deal seen as opportunistic after share price slide-analysts
* Move follows controversy over governance, internal probes
* Company has $5 bln of debt after expansion
* ENRC founders must announce intentions by May 17
By Clara Ferreira-Marques
LONDON, April 19 (Reuters) - A group of key shareholders in Kazakh miner ENRC led by co-founder Alexander Machkevitch is considering a buyout of the $6 billion company, whose shares have been battered by worries over governance and two internal probes.
The potential bid, described by analysts as opportunistic given the underperformance and sharp drop in ENRC's stock this year, sent the shares up as much as 31 percent on Friday.
In a rare statement, Machkevitch, a reclusive Kazakh-Israeli billionaire who owns a 14.6 percent stake in ENRC, said he was reviewing opportunities, including forming a bid consortium with fellow ENRC co-founders Alijan Ibragimov and Patokh Chodiev and the Kazakh government.
He said plan - which could take the company private just five years after it listed in London - was at an early stage and it was uncertain whether an offer would be made. Together, the co-founders and the Kazakh government own more than 55 percent of the company. Machkevitch declined to comment further.
The ENRC board said in a short statement that it had not yet received a proposal, and advised shareholders to take no action.
Under the UK Takeover Code, the Machkevitch group has until May 17 to either announce an intention to bid for ENRC or pull out, which would bar them from making another move for six months.
ENRC's future has been debated for months, as the company recovers from damaging boardroom battles and an aggressive, six-year acquisition spree into copper, coal and iron ore in Africa and Brazil that left it with $5 billion of debt.
Its stock is near lows not seen since the peak of the financial crisis, and it faces a January 2014 deadline to lift its free float, currently less than 20 percent, or leave the FTSE 100.
The miner has been considering proposals, including a stock issue, to stay in the index.
But sources familiar with the company say founder shareholders are reluctant to issue shares at the current, rock-bottom stock price.
Hit along with the rest of the sector by worries that Chinese economic growth is slowing, ENRC has also been weighed down by a fresh boardroom spat. According to media reports, its chairman threatened to quit last week, and its chief commercial officer, a familiar face for investors, unexpectedly left.
There are also two investigations into whistleblower allegations into potential wrongdoing, one of which, looking at Kazakh operations, has been sent to UK authorities.
"I suppose they are trying to come up with a solution that cleans everything up and takes it out of the public eye," one top-20 ENRC investor told Reuters.
"This is a very cheap company. It's an attractive set of assets that has been heavily discounted because of the corporate governance. In the structure it is in, value is not easily realised - I wouldn't want to put a number on what we would like, but I would say that the shares are very cheap."
Friday's statement sent ENRC's beleaguered shares - among the most shorted in the index - soaring, but it also boosted shares in rival Kazakhmys, which is ENRC's largest shareholder with a 26 percent stake.
ENRC closed up 26.6 percent at 291 pence, while Kazakhmys ended the day up 24.4 percent.
Kazakhmys declined to comment on Friday.
"An offer for the company appears opportunistic given ENRC shares have been very weak," Liberum analysts said in a note, adding the current level now prices in a deal. The analysts see no potential rival offer.
Commodities group Glencore has long been seen as a potential suitor for ENRC. In 2011 Glencore was forced to issue a statement denying it was considering an offer. Glencore is currently digesting miner Xstrata, acquired in the industry's largest deal to date.
Liberum also pointed to likely debt trouble ahead for the trio, which has made no comment on potential financing.
"We note that under a change of control, refinancing may be required ... while private company financing is more challenging, meaning the consortium would need a solution in this regard."
Spending last year were more than double the cash ENRC generated. The high debt and spending needed to develop ENRC's assets is likely to raise questions over potential sales, should the trio of founders and the Kazakh government decide to press ahead with their plan.
The consortium of potential bidders is being advised by Societe Generale.