German Chancellor Angela Merkel expressed concern after anti-Kremlin campaigners planning a protest near the summit venue were prevented from travelling there by Russian authorities.

"I hope that they will be able to express their opinion," Merkel told a joint news conference at the end of the two-day summit.

Putin testily defended "preventive measures" taken by Russian police ahead of the rally, comparing these to common practice in European countries, and said anti-Kremlin protestors sometimes sought to provoke police action.

The Russian leader, in turn, criticised the treatment of ethnic-Russians in EU members Estonia and Latvia as "unworthy of Europe" and accused Estonian authorities of causing the death of a Russian national during riots last month.

"They didn't just disperse demonstrators. They killed one demonstrator. He was injured and he wasn't helped so he died. We demand that the criminals be brought to account," Putin said.

Hundreds of ethnic-Russians rioted after Estonian authorities relocated a controversial Soviet war monument. Russia responded with fury to the move, while European Commission President Jose Manuel Barroso said it was "a sovereign decision."

The row with Estonia is one of many disputes between Russia and countries in formerly Soviet-dominated central Europe that joined the European Union in 2004.