UPDATE 2-Kerimov selling $3.7 bln Uralkali stake to Russian banker-reports
* Reported buyer Kogan dubbed "Putin's banker" by Russian media
* Kerimov under fire after collapse of potash cartel
* Uralkali CEO being held in Minsk, appeal for release rejected (Adds source comments about financing of possible deal)
By Megan Davies and Polina Devitt
MOSCOW, Sept 13 (Reuters) - Russian tycoon Suleiman Kerimov is selling his stake in potash producer Uralkali to investor Vladimir Kogan for $3.7 billion, a prominent Russian lawyer and news agencies said on Friday.
Shares of major European and North American potash producers jumped on speculation that a sale might lead Uralkali to rejoin an export partnership with state-owned Belaruskali, averting a possible collapse in prices for the soil nutrient.
Speculation that Kerimov has been trying to sell his 21.75 percent stake, held through his foundation, has mounted since Uralkali triggered a row with Belarus by pulling out of a cartel in July that controlled about 40 percent of the world's potash.
The reports could not be immediately confirmed but Kogan - a financier and former state official once dubbed "Putin's banker" - has been linked by media to such a deal for a week.
"If there is a deal, VTB will probably take part," said a source close to Russia's second-largest bank, VTB. Continued...