ROME, July 23 (Xinhua) -- The earliest coronavirus strains spreading in Italy's Lombardy region did not come directly from China, according to a new study.

After analyzing more than 300 blood samples of COVID-19 patients from Lombardy between February and April, researchers found that the variant of the virus is observed frequently in European countries, such as the Netherlands, Switzerland and France, but seldom observed in China, said a non-peer-reviewed paper published Monday on medRxiv.org, a preprint server for health sciences.

Italy was the first country in the world that suspended all flights from China after its outbreak of COVID-19 in December last year. But the genome sequencing suggested "a transmission chain not directly involving China," researchers led by Professor Carlo Federico Perno of Milan University said in the paper.

The researchers analyzed the whole genome sequencing of 371 samples collected from 371 patients with varying disease symptoms, ranging from mild to severe, residing in all 12 provinces of Lombardy, which has reported more than a third of COVID-19 cases in Italy.

They found the strains belong to two separate lineages, each playing a dominant role in some provinces, but they "did not contain viral strains isolated in the first months of the outbreak in China."

There could have been "multiple introductions" of the coronavirus to the Lombardy region, said these researchers, adding that these strains formed relatively isolated clusters in different areas. The viruses may have come from Central Europe, where strains with similar mutations had been detected, according to the study.

The paper suggested that these strains may have entered Italy in the second half of January, one month before the first COVID-19 case was found in Codogno, Lombardy on Feb. 20.

According to a report by Sputnik also released on Monday, Skolkovo Institute of Science and Technology (Skoltech) found that there were at least 67 coronavirus strains spreading in different Russian cities between late February and early March.

After analyzing the genome sequencing of collected samples, the researchers found that the viruses causing COVID-19 outbreak in Russia were mainly from Europe instead of China, Skoltech said to Sputnik.