Protesters in Whanganui are celebrating shutting down the courthouse during a national day of Māori action.

Te Pati Māori led a march on Parliament this morning and car convoys disrupted traffic across the North Island.

It's calling the Government's approach to Te Tiriti - and other initiatives affecting Māori - an assault.

Whanganui iwi leader Ken Mair says they'll act again on December 20, and ask all Crown agencies in the region close for the day.

He says closing the court today was a challenge to a corrupt system.

"And we'll continue to do this, as uncomfortable as it may be, towards those that want to continue to uphold that system."

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