The UN lowered its earlier toll, citing figures from the Pacific nation's disaster office.
"The National Disaster Management Office (NDMO) has confirmed 11 fatalities in Tafea and Shefa Province, including five from Tanna Island," the Office for the Coordination of Humanitarian Affairs said in a revised situation report.
Aerial assessments by military aircraft from New Caledonia, Australia and New Zealand found "severe and widespread damage", it said.
"Damage to infrastructure is limiting access to affected populations and hampering movement, however commercial flights have resumed to Port Vila," said the report dated March 16 but released today.
Prime Minister Joe Natuman today said it would be "at least a week or two" before authorities had a better sense of the destruction caused by the storm which carried winds of up to 320 kilometres (200 miles) an hour.
While initial assessors had been able to enter the eastern and western parts of the island chain, northern and southern areas were still largely unaccessible, he said.