Approximately 60 people took part in the pro-Palestine protest at Lyttelton Port on Tuesday afternoon, and police said four people were arrested about 1pm after blocking traffic.
Protesters had blocked a tunnel and poured a liquid onto the road, a police spokesperson said.
Charges were being considered.
Palestine Solidarity Network secretary Neil Scott issued a statement saying members were "repulsed" by police actions at the protest, which he labelled "disgusting".
"The police arrested seven people and pepper sprayed many, including senior citizens protesting peacefully," Scott said.
Police arrested pro-Palestine protesters, and accused the group of blocking traffic in Lyttelton, on 6 February, 2024. Photo: Supplied/ Allforallpalestine
Police "aggression" toward their activities had been increasing during that time, he said, and the group wanted an investigation into officers actions at the latest protest.
Protest organiser Ihorangi Reweti-Peters told RNZ that police used brute force to stop protesters from blocking the road.
"Police were sort of rarking people up and saying 'come on then', and 'do it'."
"Everyone was sprayed - pepper sprayed, and then the people were arrested."
Three of those arrested had been released by early Tuesday evening, Reweti-Peters said.
Acting Superintendent Craig McKay said police respected the lawful right to protest.
"But we draw a line when the safety of those involved, the public and our staff are put at risk and thoroughfares are obstructed.
"A handful of people failed to comply with police requests to move and following a number of warnings, staff utilised tactical options available to us."
He said four men aged 39, 57, 37 and 70 were taken into custody and were charged with obstructing a public place, resisting police and assaulting police.
The 39-year-old was due to appear in Christchurch District Court on Friday, and the remaining three are due to appear on Monday.
