Russian energy heavyweight Gazprom has sold a 35% stake in its Yuzhno-Russkoye gas field in western Siberia to the German chemicals group BASF.

The deal, which will see BASF’s Wintershall unit take a 35% minus one share stake in the Gazprom subsidiary Severneftegazprom, has been heralded by the Russian government as one of the most significant Russo-German agreements of recent times.

This is the first time in contemporary history that Russia has allowed a foreign partner into gas production on a gigantic field, which will be exploited for decades, said Russian president Vladimir Putin.

Yet the deal is not a one way street: Gazprom will increase its stake in the existing Wingas venture to just short of 50%, thereby increasing its exposure to the western European market, in conjunction with Wintershall.

News of the BASF venture came shortly after president Putin launched a scathing attack on Europe for demonizing Russia’s strategy on energy exports.

We are being blocked to the north, the south and the west on any pretext. We have to find outlets, to fit into the global development process.

What are we supposed to do in these circumstances, when every day we hear the same thing? We start to look for other markets, he said.

However Mr Putin was also reported to praise British prime minister Tony Blair’s stance on a possible Gazprom acquisition of Centrica. Mr Blair indicated earlier this week that his government would not stand in the way of a Russian-led approach for the company, something that Mr Putin pointed out would be counter to the UK’s pro-liberalization policy in the energy sector.