* MTS, Vimpelcom offer $4-$4.25 bln for Tele2 Russia
* VTB says its $3.5 bln deal is done, legally binding
* Fridman's A1 offers $3.6-$4 bln for the unit
* Running numbers on possible bid for Tele2 as a whole
* Tele2 and main shareholder stand by $3.5 bln VTB deal (Adds offer made by MTS and Vimpelcom, Tele2 comment)
By Megan Davies and Maria Kiselyova
MOSCOW, March 28 (Reuters) - Russian mobile companies MTS and Vimpelcom Ltd joined the bidders for Tele2 AB's Russian unit on Thursday, rivaling a proposal by billionaire Mikhail Fridman's A1 investment group and an agreed deal with VTB Bank OAO.
MTS and Vimpelcom are offering to buy the asset for $4.0 billion to $4.25 billion, including $1.15 billion of net debt, they said late on Thursday, claiming their bid was at a premium of up to 30 percent over the agreed deal with VTB.
"We would like to express our strong interest in providing an alternative offer to the shareholders of Tele2 AB and we think this is a distinctly more attractive proposal," the companies said in a joint statement citing their chief executive officers.
State-controlled bank VTB agreed on Wednesday to buy Tele2 Russia in a deal that puts an enterprise value - or equity plus debt - on the business of $3.5 billion.
A1 said on Thursday it topped VTB's offer with an all-cash bid of $3.6-$4 billion and said it was also considering an offer for the whole of the parent, Nordic telecoms group.
A1's challenge boosted Tele2 shares and raised the prospect of a rare Russian takeover fight - pitting Fridman, flush with billions from the sale of oil company TNK-BP Holding OAO , against the country's No.2 bank.
Tele2 declined to comment on the MTS and Vimpelcom offer.
"We have sold the Russian entity. We did so last night. I won't make any further comment," Tele2 spokeswoman Pernilla Oldmark said.
The Tele2 unit is Russia's fourth-biggest mobile operator after MTS, MegaFon OAO and Vimpelcom, with around 23 million subscribers in 2012. Some analysts speculated these operators or state-controlled Rostelecom could end up as shareholders.
"We concluded this deal, it is legally binding, it is done," Yuri Soloviev, VTB's first deputy president and chairman of the management board, said on Thursday.
The bank is open to bringing in strategic partners or financial backers, he added. Soloviev said VTB had not been officially approached by any of the industry players inside or outside of Russia, but would consider any proposals on merit. He wants to keep it as a whole business rather than breaking it up.
"We will spend some time thinking about strategic development and potential shareholders who would come and give us value," Soloviev said. "These could be financial, strategic, Russians, outside investors."
RUNNING THE FIGURES
A1 did not say how much it might be prepared to pay for all of Tele2, which had a stock market value of $7.5 billion at Wednesday's close.
"A price for the entirety of Tele2 is in the works - we are running the figures on a possible offer for the entire business," the spokesman said.
Stockholm-listed Tele2 said it was committed to the sale of its Russian business to VTB. The deal values Tele2 Russia's equity at $2.4 billion and includes the assumption of net debt of $1.2 billion.
Swedish firm Investment Kinnevik AB, which has a 47.9 percent voting interest in Tele2, said it was "completely behind" the sale to VTB. It was not immediately available for comment on the statement from MTS and Vimpelcom.
Some analysts, however, said the sale to VTB looked cheap. Andy Parnis at UBS said he was surprised at the low multiple paid, even with Tele2's lack of a data licence.
Tele2's Russian business has been in play since it lost out in a licensing auction for next-generation 4G services.
The sale values Tele2's Russian business in line with MTS and Vimpelcom, which trade at multiples of 4.7 and 4.3 times forecast 2013 earnings, even though it has superior growth prospects.
Tele2 investor relations head Lars Torstensson said analysts had put an average value of around 24 billion Swedish crowns ($3.7 billion) on Tele2's Russian unit, just above the sale price of 23 billion.
"We do believe this is a very fair price," said Soloviev. "The price we are paying is in line with the public market."
Barclays analyst JP Davids said the VTB deal was attractive because no regulatory issues are anticipated, whereas A1 is part of Fridman's group, which owns a stake in rival Vimpelcom.
Fridman recently closed a deal alongside three other entrepreneurs to sell their one-half stake in TNK-BP, Russia's third-largest oil company, to state oil major Rosneft for $28 billion.
His Alfa Group, of which A1 is a part, received $14 billion and has said it plans to reinvest the proceeds in telecommunications and oil projects.
Fridman, worth $16.5 billion according to Forbes, also made $5 billion last year from the sale of his stake in MegaFon.
Tele2 is being advised by Morgan Stanley. VTB is advised by its investment bank arm VTB Capital.
($1 = 6.5162 Swedish crowns) (Additional reporting by Simon Johnson, Johan Ahlander, Niklas Pollard and Leila Abboud; Writing by Megan Davies and Maria Kiselyova; Editing by Erica Billingham, David Holmes and Andre Grenon)