One person has died on the roads in Canterbury this morning, with about 25 crashes occurring since 6am.

Freezing overnight temperatures and black ice have led to treacherous conditions on the roads.

Emergency services were attending a fatal crash in Gebbies Valley which closed part of State Highway 75 between Christchurch and Akaroa about 8am.

A St John spokesperson said one person was dead at the scene when an ambulance and helicopter arrived after 7.30am.

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Another patient has been transport to Christchurch Hospital in a serious condition, he said.

No more information was known about the patient.

A Southern Police spokesman said police had attended about 25 crashes this morning.

He could not say how many of the incidents had involved collisions but said most were minor crashes where vehicles had slipped off the road.

Christchurch Transport Operations Centre said State Highway 75 would be closed until further notice because of the fatal crash.

CTOC had received a number of reports about minor crashes on the Southern Motorway and throughout Christchurch.

Motorists were urged to take extreme care due to black ice throughout the region, CTOC said.

Severe frosts overnight had led to black ice and "treacherous" conditions, Canterbury Police said this morning.

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Senior Sergeant Richard Ryan said it was expected to be busy all morning for police in Canterbury.

"It's extremely icy in Christchurch, all of the overbridges, all the main arterials and right through the city, basically everywhere, there is a lot of black ice.

"Who would know at this stage [when it's going to melt]," he said.