'Extreme concerns' for missing NT man

Authorities hold "extreme concerns" for the welfare of a man who fled the Royal Darwin Hospital while receiving treatment for a heart condition.

Police say Tristan Seela, 25, has not been seen since leaving the hospital on foot on Wednesday afternoon and he still needs urgent medical attention.

He was last seen with a canula in his left arm and police are urging anyone who may have spotted him to come foward.