ZAGREB, Croatia (AP) — The omicron variant of the coronavirus has fueled the highest number of daily new infections in Croatia since the start of the pandemic, officials said Wednesday, as other Balkan countries also reported a sharp rise in cases.

A total of 8,587 new cases were confirmed in the past 24 hours in Croatia, which presents a 50% rise since last week, Prime Minister Andrej Plenkovic said during a government session.

“The numbers show that omicron is spreading, we know it is a highly contagious variant that is present here,” he said. ”This is a warning how important it is to use everything at our disposal for protection from coronavirus."

Plenkovic said authorities will monitor the situation and discuss possible tightening of rules in the coming days. He said about 63% of adults in the population of 4.2 million people have been fully vaccinated so far.

A steep surge in new infections also has been reported in other Balkan nations following the Christmas and New Year's holidays and as the omicron variant apparently takes over. The low-vaccinated region was badly hit during the fall when the delta virus variant was dominant.

Croatia's neighbor Slovenia on Wednesday reported a seven-week high of 4,068 cases for the past 24 hours in what the official STA news agency described as a new wave fueled by Omicron.

In Montenegro, some doctors criticized lack of respect for measures such as mandatory face masks and recommendations to avoid gatherings during the holiday period. Last week, Montenegro tightened virus rules after cases started to rise, including limited working hours of bars and a ban on any gatherings.

In Serbia, long lines have formed outside COVID-19 medical centers as infections started to soar following New Year's celebrations with open air concerts and packed bars, restaurants and clubs.

Experts have warned that new cases could reach “dramatic” figures in the coming days because of the omicron variant and disrespect for COVID-19 rules. The state RTS television quoted unnamed health ministry officials as saying that “this is just the beginning of a new wave that apparently is going to be very hard.”

Serbia and most countries of Central and Eastern Europe have about 50% of the population fully vaccinated, which is far lower than the European Union average.

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