Venice: The number of new coronavirus cases reported outside China has exceeded the number of new ones in China for the first time, as a top official warns that prematurely declaring a pandemic could "paralyse" global efforts to contain the outbreak.

World Health Organisation director-general Tedros Adhanom Ghebreyesus revealed there were 412 new cases in China as of Thursday morning (AEDT) compared to 459 confirmed infections in other countries, a milestone fuelled by major clusters in Italy, Iran and South Korea.

In an update to affected nations, Dr Ghebreyesus repeated his view that the spike in cases in Europe, Asia and the Middle East was "deeply concerning" but pushed back against the option of declaring COVID-19 a global pandemic.

"We should not be too eager to declare a pandemic without a careful and clear-minded analysis of the facts," he said.