The WHO warned it could take weeks to determine how infectious the variant is, whether it causes more severe illness and how effective treatments and vaccines are against it.
'We're going to get the answers that everybody out there needs,' WHO emergencies director Michael Ryan said.
The WHO earlier said it had still not seen any reports of deaths related to Omicron, but the new variant's spread has led to warnings that it could cause more than half of Europe's Covid cases in the next few months.
The new variant could also slow global economic recovery, just as the Delta strain did, International Monetary Fund chief Kristalina Georgieva said on Friday.
'Even before the arrival of this new variant, we were concerned that the recovery, while it continues, is losing somewhat momentum,' she said.