A herd of 15 wild Asian elephants are continuing their long journey from their forest home in Xishuangbanna National Nature Reserve in southwest China's Yunnan Province.

They started marching north and so far they have covered 400 km. They are now within 20 km of the provincial capital of Kunming, which is set to hold a UN Biodiversity Conference in October.

Drones have been deployed by local authorities to monitor their migration and fire trucks are used to keep them out of populated city center areas to avoid encounters between residents and the elephants.

There were originally 17 elephants that left the nature reserve, but two gained access to alcohol at a villager's home and the pair decided to head back.

However, what made these endangered animals leave their habitat and march north is still a mystery. The suggestion is that they are on the search for food and have become bolder as they have discovered there can be food supplies in and around human settlements.

Watch Ma Ke's full report for CGTN Europe:

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Video: Elephants head down a city highway