Germany issued a warning against travel to parts of Croatia on Thursday as Europes largest economy battles to contain a rising number of coronavirus cases during the summer season. The German foreign ministry advised against travel to the regions of Sibenik-Knin and Split Dalmatia, which are popular with tourists, after the public health agency declared them coronavirus risk regions, making tests for returnees mandatory. The number of new cases in Germany has been rising steadily since early July and has accelerated in recent weeks. On Thursday, the number of confirmed cases climbed by 1,707 to 228,621, marking their biggest daily increase since April 26. Imported cases of the coronavirus have risen to 39% of overall new infections in Germany this week, up from around 30% last week, Reuters reported. Croatia is the source of the third-highest number of infections among people returning to Germany, after Kosovo and Turkey, according to data from the Robert Koch Institute for infectious diseases. Concern is growing that people may be getting infected while visiting family members in those countries. Statistics from the health ministry in North Rhine-Westphalia, Germanys most populous state and hit relatively hard by the pandemic, found more than a third of returnees who tested positive for coronavirus between July 1 and Aug. 16 came from Kosovo, with Turkey in second place at almost 20%. Those returning from more traditional holiday countries, such as Spain and Greece, made up just 2.5% and 0.5% of positive cases in the state, respectively. Germany also urged people not to travel to the Valcea region of Romania, but removed a warning for the regions of Ialomita, Mehedinti and Timis. It also lifted a travel warning for Luxembourg.