The World Health Organization opened its first summit on traditional medicine Thursday, with the group saying it was seeking to collect evidence and data to allow for the safe use of such treatments.

Traditional medicines are a "first port of call for millions of people worldwide", the UN health agency said, with the talks in India bringing together policymakers and academics aiming to "mobilize political commitment and evidence-based action" towards them.

"WHO is working to build the evidence and data to inform policies, standards and regulations for the safe, cost-effective and equitable use of traditional medicine", WHO chief Tedros Adhanom Ghebreyesus said as he opened the summit.

Traditional medicine could boost healthcare "access gaps", but was of value only if used "appropriately, effectively, and above all, safely based on the latest scientific evidence", Tedros warned earlier.

The two-day WHO Traditional Medicine Global Summit takes place alongside a meeting of G20 health ministers in the Indian city of Gandhinagar.

"We need to face a very important real-life fact that traditional medicines are very widely used," Nobel laureate and Chair of WHO Science Council Harold Varmus told the summit via video link.

"It is important to understand what ingredients are actually in traditional medicines, why they work in some cases... and importantly, we need to understand and identify which traditional medicines don't work".

The summit, set to become a regular event, follows the opening last year of a WHO Global Centre for Traditional Medicine, also in India's Gujarat state.