When Putin was speaking about proposals from NGOs to the Group of Eight industrialized nations to close their nuclear power plants, a number of young people wearing black t-shirts emblazoned with the slogan "No to NPPs" stood up.
The Russian leader said he did not fully support a complete end to nuclear power, but did say that alternative sources of energy should be developed and made available.
Putin said he backed a demand made by NGOs that G8 leaders allocate funds to develop alternative energy sources. He said governments should provide money to achieve this objective, but without increasing taxes for producer companies.
"Increasing the tax burden is not always the best way because even I cannot be sure that the funds will be spent to accomplish these goals," he said.
The organizers of the two-day international NGO forum said earlier that the Civil G8 - 2006 would discuss matters of concern for the international community ahead of the July 15-17 summit of G8 leaders, adding that NGOs could draft proposals to be considered when setting out agendas for further summits.
Russia is presiding over the club of rich nations this year and the leaders of the United States, the United Kingdom, Japan, Canada, France, Germany and Italy will be joining Putin in St. Petersburg for Russia's debut summit on July 15-17.
Over 700 people representing prominent rights organizations, including the International Helsinki Group, Greenpeace, Amnesty International, Charities Aid Foundation, and others, are attending the NGO forum in the Russian capital.
A Kremlin source said earlier Tuesday that a new Russian law on public organizations, effective from April, would be the focus of the forum's discussion. The law set more stringent and complicated financial reporting requirements for NGOs and has been criticized in the West and liberal groups in Russia as being too restrictive.
Lawmakers and political scientists in Russia have claimed that NGOs helped "color revolutions" in neighboring ex-Soviet countries, particularly Ukraine and Georgia, which swept away the ruling elite in favor of West-leaning authorities in 2004 and 2003.
But Russia has been consistently defending the new legislation saying that it had been prepared with recommendations of European legal experts and had been thoroughly studied by the Council of Europe's officials.