Tedros Adhanom Ghebreyesus voiced alarm at the conflict which erupted Saturday with US-Israeli attacks on Iran, and warned that the "impact goes beyond the immediately affected countries".

"Operations at WHO's logistics hub for global health emergencies in Dubai are currently on hold due to insecurity," he told a press conference.

Last year, the logistics Dubai hub processed more than 500 emergency orders for 75 countries around the world, Hanan Balkhy, the WHO's Eastern Mediterranean regional director, told reporters.

"Humanitarian health supply chains are now being jeopardised," she warned.

Balkhy explained that "the hub's operations are temporarily on hold due to insecurity, airspace closures and restrictions affecting access to the Strait of Hormuz".

The disruption, she said, was "preventing access to $18 million in humanitarian health supplies while another $8 million in shipments cannot reach the hub".

It was affecting more than 50 emergency supply requests from 25 countries, as well as some $6 million in medicines destined for the Gaza Strip.

And, she cautioned, $1.6 million in polio laboratory supplies were being held up, which could have dire impacts for Afghanistan and Pakistan, where the disease is endemic.