Serbian President Aleksandar Vucic greeted Chinese doctors who arrived in Serbia on Saturday, kissing the Chinese flag in a show of gratitude for the country's timely support against COVID-19.

"The arrival of Chinese health professionals is of great importance to us because they were the first to defeat the great enemy of today: COVID-19," Vucic said.

"Everything on this plane is free-of-charge assistance, a donation from the People's Republic of China. We should thank them with all our hearts, they have proven to be great friends of Serbia and Serbs," he added.

Serbia's largest aircraft, an Airbus A330, landed in from China with the largest shipment of aid to Serbia which includes medical devices, such as respirators, face masks, anti-microbial medical gowns, and security equipment, as well as six Chinese experts.

The medical aid packages that came from China read in Chinese language and in Cyrillic: "The friendship of steel, we share weal and woe!" with a heart that had the flag of Serbia on one side, and the flag of China on the other.

Chinese President Xi said in a letter received by Serbian President Vucic that China supports Serbia's efforts to fight the coronavirus and will provide the country with material and medical assistance, provide support in procuring essential goods from China, as well as professional assistance.

China's ambassador to Belgrade, Chen Bo, said the aid was a sign of the "iron friendship" between the two countries. 

"They (the Chinese doctors) have come from the frontlines of China's fight against the virus. And right away, they came to Serbia to the new frontline. Please allow me to express high respect and gratitude to them in the name of all the Chinese citizens who live and work in Serbia," the ambassador said.

Serbian authorities have reported 171 people who have tested positive for coronavirus and one related death.

The government introduced tighter measures on Friday including closing down cafes, restaurants and parks and enacted a curfew from 8 p.m. (1900 GMT) until 5 a.m. (0400 GMT).

In the capital Belgrade, even police helicopters are being used to try to stop the spread of the coronavirus. During the curfew, they are patrolling the skies trying to find those in breach of imposed restrictions. And from Monday, all the restaurants and coffee shops throughout the country will be shut.

Vucic said that one of the halls at Belgrade Fair will be turned into a hospital with 3,000 beds to accommodate people infected with coronavirus.

(CGTN's Aljosa Milenkovic also contributed to the story.)