Russia to spend $500 million to reinforce Caucasus border

"We will seal the border by the end of 2007," Putin said during a televised question and answer session on Wednesday.

A high level of security on Russia's southern border is among the requirements Russia must meet to switch to visa-free travel with the European Union.

Russia's immigration policy should also be adjusted, Putin said. "By the way, the number of illegal immigrants in this country is estimated at from 10 to 15 million," Putin said.

About the same number of illegal immigrants are in West European countries, he said. Interfax