Under the new rules, masks are mandatory in all public buildings and only essential shops will be open at weekends.
Latvia has declared a three-month state of emergency after a record surge in COVID-19 infections.
Under the new rules, masks are mandatory in all public buildings, and all public employees must be vaccinated by 15 November.
Latvians who are not vaccinated will not be allowed to enter supermarkets from Monday.
Only essential shops will be open at weekends, while all citizens have been encouraged to work from home where possible.
The number of daily coronavirus cases in Latvia has risen above 1,000, a higher infection rate than earlier this year. Latvian hospitals are already overcrowded with Covid patients.
"Please do not crowd, do not socialise and reduce your contacts," tweeted Latvian Prime Minister Krišjānis Kariņš.
"For those who have not yet been vaccinated, please go and get vaccinated. Let's be patient, purposeful, and responsible."
Only 48% of Latvians are fully vaccinated against COVID-19 — the fourth-worst vaccination rate in the European Union after Bulgaria, Romania, and Croatia.
"We are forced to turn away other patients with non-life-threatening diagnoses," Karlis Racenis, head of the Latvian Junior Doctors’ Association, said at a press conference.
"Emergency medical teams cannot even answer all the calls," he added.