A man is in critical condition following a crash on one of New Zealand's major highways.

Two cars have collided at the bridge on SH1, north of Turangi at 6.25am.

"A man is in a critical condition in one of the vehicles.

"The road will be closed while police and emergency services are at the scene."

Diversions will be in place, so motorists are asked to seek alternate routes.

Reports of a crash on #SH1 just north of Turangi. Please follow directions of emergency services. Road closure is likely. Expect delays/diversions. More to follow. ^TP

— NZTA Waikato/BoP (@NZTAWaiBoP) August 5, 2018

Meanwhile, SH2 - between Taneatua and Waimana - in the Eastern Bay is closed.

The NZTA says a slip in the gorge has forced the roading agency to close the highway in both directions.

"Motorists are advised to expect delays in the area and consider an alternative route."

SH2 from Matata to Paengaroa is also closed due to slips and flooding following heavy rain from overnight.

More heavy rain is being forecast for today, with a severe weather warning in place in the Bay of Plenty.

Read more here.