“We must be a bit stricter in places where infection chains spread mostly, which is parties and, unfortunately, also travel,” the chancellor’s chief of staff, Helge Braun, told public broadcaster ARD.
“We are at the beginning of a second wave and only the politicians’ and the population’s determination will decide whether or not we can avoid it, or slow it down,” he added.
Germany had managed to keep the number of new infections and deaths lower than many of its neighbours but the daily number of new cases has leapt above 4,000 since Thursday, the highest since April.
Sunday’s count was below that but that is because test reports tend to be lower at weekends.
Merkel and mayors from Germany’s 11 largest cities agreed on Friday (9 October) to adopt stricter measures if infections exceed a threshold of 50 cases per 100,000 population in a week.
More than 20 cities are now above that level, which has caused a patchwork of internal travel restrictions.
Braun, a medical doctor, said test centres should prioritise health sector workers and people showing symptoms over tourists.
Holidaymakers can circumvent the local travel curbs if they produce negative test results.
Bavaria’s prime minister Markus Soeder at the weekend proposed steeper fines for people not wearing masks where mandated in places such as public transport and shops of €250 ($295.60) compared with the current €50, and €500 for repeat offenders.
Braun said he agreed with tough penalties.
Merkel will hold further talks with state premiers on Wednesday.