A man has been left with burns to his mouth after an assault outside Nelson City Council offices early this morning.
The man suffered solvent burns to his mouth and throat in the attack, which happened around 6.45am, police said.
The man was taken to Nelson Hospital, where he remained this afternoon, police said.
The attack was being treated "extremely seriously", Constable Nick Kempthorne said.
"This is a cowardly attack with potentially serious consequences and we are very keen to find out who is responsible," he said.