Two bushwalkers have been killed and three others trapped in debris after a group of bushwalkers were swept off a cliff by a landslide in New South Wales’ Blue Mountains.

An urgent rescue effort is under way at Wentworth Pass, near Wentworth Falls, after emergency services were alerted to the landslip about 1.40pm on Monday afternoon.

Three walkers are in the care of paramedics at the scene, as efforts to extract them continue.

Two are being treated for critical injuries.

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NSW Police told a press conference on Monday evening that a man and a boy had died, and that a woman and boy were in a critical condition with head and abdominal injuries.

Acting Superintendent John Nelson said it was unknown if the walkers were locals or tourists, but the fifth member of the group – a girl – could potentially walk from the site.

Chaplains are also on site to provide emotional support to the injured and emergency workers.

Acting chief superintendent of NSW Ambulance Stewart Clarke said the extraction had been difficult from the site – about a 90-minute walk from Wentworth Falls – in “an extremely dangerous and extremely unstable” environment.

He hoped the injured could be freed before nightfall and transferred to hospital once safely sedated and incubated.

Two PolAir helicopters are on the scene assisting in the rescue effort, as well as specialist police, SES and National Parks staff, and NSW Ambulance crews, including a critical care doctor and a critical care paramedic.

-with AAP