The tally of active cases of the new coronavirus has risen to 4,764, above the previous high of 4,737 seen in April, health ministry data showed on Sunday.
On Saturday 113 new cases were identified, bringing the total since the beginning of March when first cases were found to 13,885.
The central European country of 10.7 million has had 358 deaths from the Covid-19 disease caused by the coronavirus, far fewer than many western European nations.
The rise in active cases has grown as daily infections held above 100 in the past days, outpacing the number of recoveries. The new cases -- many in the country's industrial north-east where a mine outbreak occurred -- have so far been milder than before.
The number of people in hospitals was 135 on Saturday, less than a third of the peak of 446 in April and far below capacities of the national health system as presented by the government.
Pressure on hospitals is among criteria the government uses when deciding on response.
Since lifting a strict nationwide lockdown imposed in March, the authorities have pledged to avoid future countrywide measures and instead respond to local outbreaks regionally.
On Friday, authorities tightened coronavirus restrictions in the northeast of the country after a spike in cases in several locations, reinstating compulsory face coverings, limiting restaurant opening hours and ordering checks on cross-border commuters.