President Francisco Sagasti said the increase in infections had pushed hospitals close to collapse. The lockdown will run from 31 January to 14 February, covering 10 regions.
The new restrictions include a closure of all non-essential shops, a ban on domestic air and land travel and the extension of a ban on flights coming from Europe to flights from Brazil in an attempt to curb new, more contagious strains of the virus.
The country has reported more than one million cases and about 40,000 deaths related to Covid-19, according to data from Johns Hopkins University.
At the start of the pandemic, Peru imposed one of the earliest and strictest lockdowns in Latin America to stop the spread of the virus. But the measures had limited impact because of the country's poor healthcare system and several social and economic factors, including the lack of social distancing in overcrowded cities.