It comes as infections in the region continue to rise, forcing countries to lock down borders and close schools.
The WHO's South East Asia region contains 11 countries, almost all of which have now recorded virus cases.
It includes Indonesia, Sri Lanka, Thailand, Bangladesh and North Korea.
Dr Poonam Khetrapal Singh, Regional Director of the WHO South East Asia region, said on Tuesday that "more clusters of virus transmission are being confirmed".
"We clearly need to do more, and urgently."
What's the situation in the region?
Many regional countries outside the WHO's definition of South East Asia have had a slow response to the outbreak, only taking drastic measures in recent weeks or days as the number of cases continue to grow.
Malaysia, which now has the highest number of cases in the region, did not put any strict social distancing measures in place until it had a huge leap in the number of cases.
Most of the country's infections have been linked to a religious gathering that was attended by around 16,000 people.
Malaysia has now locked down its borders, banning the entry of all travellers. Schools in the country have also been closed.
In nearby Indonesia, which according to John Hopkins has 172 recorded cases of the virus, President Joko Widodo admitted recently that he deliberately held back information about the spread of the virus to prevent panic.
The Philippines' Rodrigo Duterte had earlier in February joked that he wanted to "slap" the virus. The Philippines has now introduced sweeping quarantine measures that have left millions confined in the capital, Manila.
Myanmar and Laos have both not reported any cases of the virus - though experts have seriously doubted the credibility of this.
A spokesperson for Myanmar's government claimed that people's "lifestyle and diet" have protected them from the virus.
There are also no cases of the virus in Timor-Leste.
What has the WHO advised?
The WHO has said the numbers coming out of South East Asia show that "some countries are clearly heading towards community transmission of Covid-19".
It called for continued efforts to "detect, test, treat, isolate and trace contacts".
Dr Khetrapal Singh said "practicing social distancing [could] not be emphasized enough... this alone has the potential to substantially reduce transmission".
"We need to act now," said Dr Singh.
What's the situation worldwide?
According to John Hopkins, there are now 197,139 confirmed cases worldwide, with 7,916 global deaths recorded.
The main bulk of deaths come from China, where the virus first emerged last December.
But the virus is now spreading faster outside China than inside, with a lot of the focus moving to Europe, where cases have spiked over recent weeks.
The EU has now ban travellers from outside the bloc for 30 days, as cases continue to soar in Italy and Spain.