Protesters have made makeshift structures and are blocking the entrance to Ravensdown fertiliser plant in Dunedin this morning.
About 15 protesters gathered at the two entrances to the plant in Ravensbourne about 9am and police arrived at the scene not long after.
The protesters are blocking the entrances and have made makeshift wooden structures to make it harder for them to be moved on.
Ravensdown Group communications manager Gareth Richards confirmed it was receiving a shipment of phosphate rock from Western Sahara "which the UN designates as sovereignty undecided".
He said the shipment was estimated to arrive later next week depending on tides and unloading times.
"We should appreciate the ship’s arrival because thousands of jobs throughout Otago and the rest of New Zealand depend on the movement of agricultural inputs and outputs.
"As an essential service, Ravensdown is working hard to help farmers grow the food for export that earns the dollars that subsidise NZ’s social and economic recovery.
"So it’s hugely disappointing to see a handful of localised protesters continuing to wilfully ignore the other side of the story."
The issue remained complex, in a volatile part of the world, and Ravensdown supported the efforts by the UN to seek a political solution, he said.
Environmental Justice Otepoti spokeswoman Abby Spilg-Harris said in continuing to purchase and import the phosphate Ravensdown were financially supporting the continuation of a military occupation of Western Sahara, and oppression of the Saharawi people.
"Ravensdown have blood on their hands.
"118 countries recognise this as a gross human rights abuse but we still don't."