KIEV, March 26 – Ihor Kolomoyskiy, the third-richest Ukrainian, has started talks seeking to buy a 50% stake in RosUkrEnergo, a controversial Swiss-based supplier of natural gas to Ukraine, an online newspaper reported Wednesday.

Kolomoyskiy seeks to buy out two Ukrainian shareholders, Dmytro Firtash and Ivan Fursyn, who respectively own 45% and 5% of the gas trader. Gazprom of Russia owns the remaining 50% in the trader, and controls its management.