Raw video : Greenpeace activists on Thursday protested Russian Prime Minister Vladimir Putin's offer to help Turkey build nuclear power plants.

Hours before Putin was expected to sign a nuclear energy deal in Ankara, about 20 protesters unfurled a banner that read "No to Atom please" in the city's downtown area.

They displayed mock nuclear reactors and atomic bombs, as well as giant matryoshka nesting dolls painted with the faces of Putin and Turkish Prime Minister Recep Tayyip ErdoÄŸan -- in an effort to suggest nuclear power issues hold hidden surprises.

Hundreds of riot police surrounded the protesters.

Russia's Atomstroiexport was the only company to bid to build Turkey's first nuclear power plant, though no final decision has been made.

Turkey, which says it needs nuclear technology to meet its growing energy needs, has said Atomstroiexport was technically qualified to do the job.