Latvia has introduced strict new laws on citizenship which require people to have a good knowledge of Latvian.
Ethnic Russians protest against the tough citizenship requirements
Under the new laws citizenship will be refused if the candidate fails a language test three times.
Latvian was reinstated as the official language following independence from the Soviet Union in 1991.
More than 20% of the population still speaks Russian as their mother tongue and more than 400,000 people have not been granted citizenship.
During almost 50 years of Soviet rule, thousands of Latvians were deported to labour camps in Siberia, while hundreds of thousands of Russians, Belarussians and Ukrainians settled in Latvia.
The vast majority of the people without citizenship are ethnic Russians.
They have been described officially as "non-citizens" and are not entitled to a European Union passport, although Latvia joined the EU in 2004. They do not have voting rights either.
The new rules are likely to make the naturalisation process more difficult by raising the level of the required exams.
"Quite a lot of people come to the language exam without any preparation," Liga Lukso, a spokeswoman of the naturalisation board, told AFP news agency.
"It shows their lack of serious attitude towards Latvian citizenship."
The amendments adopted by the government do not need to be approved by parliament.