In a letter seen by Reuters, Kasparov, 50, said Latvian citizenship would give him the security to work "in Russia and in other countries across the world where civil rights are denied and democratic norms are trampled on".

Kasparov, a veteran opposition leader in Russia and a well-known critic of President Vladimir Putin, has in recent years spent much of his time abroad. He said the mother of his son, Vadim, was a Latvian citizen and he had won an important chess victory in the former Soviet state when he was seven years old.

"Every Latvian has the right to express his opinion freely, participate in the political process and not be afraid of unlawful persecution," Kasparov wrote of the Baltic state.

He said he wanted to retain his Russian citizenship as well, said Laila Timrota, spokeswoman for the ruling coalition party Unity in Latvia.

The letter, written in Latvian, was addressed to all parties and independent members of parliament except for the Harmony Centre party, said Andrejs Klementjevs, a member of parliament for the party.

The Harmony Centre party signed a cooperation agreement in 2009 with the United Russia party founded by Putin.

(Reporting by Aija Krutaine via Stockholm newsroom, editing by Elizabeth Piper)