Volunteers transform Ukraine's Odesa catacombs into liveable bomb shelter to protect civilians from Russian attacks

Odesa has an underground tunnel network spanning thousands of kilometres. (Supplied: Roman Mauser)

A group of volunteers from the southern Ukrainian port city of Odesa have taken their fight to save lives underground into one of the world's largest labyrinths of catacombs. 

Descending more than 20 metres deep into the dark, forgotten tunnels, the group has been working to turn sections of the tunnels into liveable bomb shelters.