OMV, the Austrian energy and chemicals group, on Monday drew a line under its two-year struggle to buy rival Mol of Hungary by selling its 21.2 per cent stake to a cash-rich Russian oil group loyal to the Kremlin.

Yet, the €1.4bn ($1.8bn) sale to Surgutneftegaz – at more than double the market value – immediately sounded alarm bells in Hungary, where Mol had fought to guard its independence, and Brussels, where European Commission energy officials expressed concern it could undermine recently revived efforts to develop a united European Union energy policy.