A 16-year-old New Zealand citizen has died in a car crash in Tonga - in the rental car his father was using, having just arrived from New Zealand to visit his son.

Tonga Police confirmed the teenager was one of two young men killed following a horrific car crash with another vehicle on the island of Vava'u over the weekend.

Emergency services were called to an intersection about 6am (local time), on Sunday, after reports of a collision.

"The 16-year-old passenger died on impact," Police said in a statement, "while the 22-year-old driver was rushed to the hospital with very severe injuries; where he died a few hours later."

The two young men are cousins, authorities said.

'A very sad visit for the father'

Tonga Police media officer Baba Lehā told the Herald the teenager had been in Tonga for some time and that his father had arrived from New Zealand last week on Monday.

"The father was visiting the son in Vava'u," she said.

"It is now a very sad visit for the father."

Lehā said the 16-year-old was a Kiwi citizen who had been sent to Tonga to go to school.

He had been living with his uncle - his father's brother - and his family, which included the 22-year-old driver.

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The vehicle the cousins had been in was a rental car that had been rented out by a relative, but which was being used by the teenager's father, Police said.

Authorities confirmed that speed was the contributing factor in the crash.

Police said investigations show the driver of the rental car lost control of the car, which then hit the other vehicle involved before smashing into an electrical pole.

The driver of the second vehicle suffered severe leg injuries and was rushed to hospital for treatment.

The 60-year-old had just been at a morning church service before the crash happened. He is said to be recovering in hospital.