The crash at the intersection of Brougham St and Waltham Rd in Sydenham happened about 3.30am.
A St John spokesperson said one person has critical injuries, another is in a serious condition and three have moderate injuries.
All were taken to Christchurch Hospital by ambulance.
The right turn from Waltham Rd onto Brougham St is currently blocked while a power pole is being replaced.
Motorists are advised to take care but can still travel north and south on Waltham Rd.
The circumstances of the crash and whether or not speed or alcohol were factors are not yet known.
"However, it is critical that people drive sober and we always strongly urge this."
The NZ Transport Agency said part of the road will be closed until further notice.
"Take extra care along this route," the NZTA said.
Additional reporting NZ Herald