"The risk is so great now and the numbers are so frightening – it seems likely that we have tens of thousands of infected people," she told the Ziniu Radijas radio station.
This is indicated by the high proportion of positive tests, according to the prime minister.
"Given the scope of testing we have now and that up to 20 percent of the test results are positive, we can state that testing no longer shows anything about the real situation," Simonyte said.
"We just don't know how many people are ill," she added.
The prime minister warned people to follow the lockdown rules or face a new wave of COVID-19 in January.
"If the majority of people follow the lockdown restrictions, we could expect (the daily count to decline to) 500-700 new cases in late January, which would be a great relief for our health system, too", she said.
"If people opt to think about how to bypass these restrictions during Christmas – and, obviously, we can't put a policeman in every home – this means that that we'll have another significant wave in January, which will put a lot of strain on the health system," she said.
Lithuania is currently one of the most coronavirus-affected countries in Europe and worldwide.