The rallies have closed schools and halted transport
Thousands of protesters are continuing demonstrations in Chisinau, paralysing the capital of the former Soviet republic of Moldova.
They are demanding the resignation of the country's communist president, Vladimir Voronin, and the holding of new parliamentary elections.
Police and interior ministry troops have been put on alert, and President Voronin has warned that force will be used to quash the protests.
Russia, which welcomed the election of Moldova's communist authorities, has called for restraint.
Several thousand demonstrators have gathered daily since Sunday, when more than 50,000 Moldovans gathered to voice their demands.
Public transport is blocked and many schools are closed.
Desperate economy
The protests started earlier in the year and were sparked by the reintroduction of compulsory Russian-language lessons in Moldova, where most people are Romanian speakers.
The opposition says the communists have been unable to improve the desperate economic situation in Europe's poorest country - and would rather suppress dissent instead.
But the demonstrations had dwindled until the disappearance of a well-known opposition politician, who had been a key force in the anti-government rallies.
And now the demonstrators' demands include the resignation of President Voronin and his government.
They have set up tents outside the country's parliament building and in a city-centre park.
Regional embarrassment
Talks between the main opposition party and the authorites have failed, and the authorities have threatened to use force.
But the loyalty of the security forces is not guaranteed, and it seems unlikely that they would obey orders from the communist government to end the protests.
Events in Moldova are a particular embarrassment to Russia.
The Kremlin welcomed the election of pro-Russian communists in Moldova, hoping to retain some influence in this corner of south east Europe.
But against the background of the continuing protests, Russia has avoided open support for President Voronin, leaving him looking increasingly isolated.