Emergency services were called to the accident on State Highway 1, in the central North Island's Rangipo Desert region, about 5.35pm today.
A St John Ambulance spokesman said six people were believed to be seriously injured, while two others suffered moderate injuries.
Fire crews were working to rescue people still trapped in the vehicles, while six ambulances and two rescue helicopters have been sent to the scene.
Meanwhile, police have named the man who was killed when his car crashed on a Far North road last night.
Wiki Antony Brass, 50, died after his car rolled off the road and into a drain on Ahipara Rd, about 14km southeast of Kaitaia, at about 8.40pm.
He was the sole occupant.
The accident came less than two hours after one person died and five others were badly injured when a car and a 4WD collided in the eastern Bay of Plenty.
The impact of the crash, which happened at the intersection of SH34 and Park Rd in Putauaki, about 27km southwest of Whakatane, sent one car into a power pole, cutting off power in the area.
Emergency services arrived at the scene to find the car alight, and one of its occupants dead. Two other people travelling in the car were also seriously injured, including a 27-year-old man who was flown to Tauranga Hospital in a critical condition.
In the second vehicle, an 11-month-old baby suffered serious head injuries and was taken to Auckland's Starship hospital, while a 22-year-old man with severe burns was flown to Waikato Hospital. He was in a serious condition in the hospital's intensive care unit this morning.
A woman travelling in the car was taken to hospital by ambulance.
The accidents followed two fatal crashes in the Waikato on Good Friday.
James Victor Robinson, 18, of Morrinsville, died after his car went off the road and into a nearby paddock before crashing into a bank near Wardville Rd in Waharoa, 53km east of Hamilton.
Nearly two hours later, a collision between a truck and car on Gordonton Rd in Taupiri, 26km northwest of Hamilton, left a 60-year-old woman dead and several others with critical injuries.
Last year over the Easter holiday period, seven people died and 191 were injured on New Zealand roads.
The official Easter holiday period began at 4pm Thursday and runs until 6am Tuesday.
