Tongan protesters have scuffled with New Zealand police outside a residence of the king of Tonga in the northern city of Auckland.
Despite appearances, Tonga's strike shows no signs of abating
Civil servants on the impoverished South Pacific archipelago have been on strike for several weeks.
A blaze engulfed one of the king's houses on Tonga on Monday, although it was not clear if this was related.
New Zealand has said it will send a negotiator to Tonga to mediate between the government and civil servants.
Some 3,000 government employees have been on strike since July, demanding pay increases.
The unrest is now spreading to Auckland's large Tongan community.
About 50 Tongans were involved in the clashes with police and royal staff outside the residence of 87-year-old King Taufa'ahau Tupou in the town on Monday.
They demanded to meet the king but were blocked by 30 police officers.
Reports said two men and two women were arrested after the scuffles.
New Zealand Foreign Minister, Phil Goff, said the strike was having a significant impact on Tonga's economy.
"It is important that a process is put in place to help resolve the issues and reduce tensions in Tongan society," he said according to the French news agency AFP.
Tonga's civil servants launched their protest after senior government officials were awarded pay rises of up to 80% in July.
They have rejected offers by Tonga's authorities to increase their wages by a third.