The German government has sought to distance itself from the country's former chancellor Gerhard Schroeder after he was reported to have partied with Russian President Vladimir Putin despite tension between Berlin and Moscow over the crisis in Ukraine.

German media report that Schroeder attended a meeting Monday in St. Petersburg, Russia, of gas pipeline operator Nord Stream AG, of which he is board chairman.

After the event Putin reportedly turned up for a celebration in honor of Schroeder's 70th birthday.

A senior German official, speaking on condition of anonymity in line with protocol, stressed Tuesday that Schroeder wasn't in Russia on behalf of Angela Merkel's government.

Schroeder, who was chancellor from 1998 to 2005, is said to have a close relationship with Putin, once calling him a "flawless democrat."