A few thousand people took part in a Moscow rally to support a pro-science foundation under pressure from the government.
The rally on June 6 comes two weeks after Justice Ministry officials put the private Dynasty Foundation -- a top sponsor of science in Russia -- on its list of foreign agents.
Any NGO that receives foreign funding and is deemed to be involved in politics must register as a foreign agent under controversial legislation signed by Putin in 2012.
Protesters at the central Moscow rally included scientists and intellectuals as well as opposition activist Aleksei Navalny.
Many held signs with slogans such as "Nobel laureates are foreign agents" and "Putin cannot solve problems, he is the problem."
Dynasty head Dmitry Zimin, 82, whose fortune funds the foundation, has threatened to close it because it was placed on the foreign agents' list.
Astrophysicist Boris Shtern told rally participants that: "Alas, science is slowly dying. The massive advance of ignorance is being supported by the media and authorities."