Cases have risen since the country held parliamentary elections in mid-June.
Serbia has tightened COVID-19 restrictions again after recording its highest spike in coronavirus cases since April.
Three hospitals in Belgrade, after a break of just a month, have been transformed back into coronavirus-only facilities.
"The beds fill up at an express speed as soon as they are made available to patients with COVID-19," a doctor from one of the hospitals told AFP on condition of anonymity.
After coming through the first wave of the epidemic in early May, Serbia has seen a resurgence in the number of cases, officially rising from around 50 daily infections a month ago to more than 350 today.
The country had lifted lockdown measures allowing large gatherings such as sports matches to take place without social distancing.
That included including a tennis tournament organised by Novak Djokovic, who tested positive a few days later.
Serbia was the first country in Europe to hold an election after the lifting of lockdown measures and since then, several government officials including the defence minister have tested positive for the virus.
There have been a total of more than 15,000 cases and just under 300 deaths in the country since the beginning of the epidemic.
It comes amid rising concerns about cases in eastern Europe and the Balkans.
Virus cases continue to rise in the United States
Across the Atlantic, coronavirus cases are rising in 40 out of 50 US states, as the country confirmed more than 50,000 new cases of the virus in a single day, breaking its previous record.
The southern state of Florida confirmed 10,000 new cases of coronavirus in a single day and 67 deaths as outbreaks in several western and southern US states have worsened.
The rise in cases in the US is largely attributed to a fast easing of social distancing measures in several states and a lack of social distancing.
States that were largely spared from the virus outbreak in March and April are now seeing exponential rises in cases.
The government reported meanwhile that US unemployment fell to 11.1 per cent in June as the economy added 4.8 million jobs. But this was before states began pausing reopening due to new outbreaks.
The outbreak in the US has meant rethinking some of the easing of lockdown measures.
New York City decided to delay reopening bars and restaurants indoors in order to curb the spread of coronavirus after limiting the spread of the virus significantly. California, which has seen a recent rise in cases, also closed bars and indoor restaurants across much of the state on Wednesday.
Research has shown that cases can be linked to dining indoors at a restaurant or bar.
A study of COVID-19 in Japan noted many clusters "were associated with heavy breathing in close proximity, such as singing at karaoke parties, cheering at clubs, having conversations in bars, and exercising in gymnasiums."
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