Two US firefighters are shot dead and two injured while responding to an emergency call in upstate New York.

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Police in upstate New York say a gunman who "trapped" and shot four volunteer firefighters outside a blazing home in western New York State is dead.

Police Chief Gerald Pickering said two of the firefighters were killed and two others hospitalised after the ambush on Lake Ontario north east of Rochester.

He also said the gunman is dead and an off-duty police officer who was driving by suffered shrapnel injuries. One of the dead firefighters is also a town police lieutenant.

Police also confirmed four homes in all were destroyed and four damaged by the spreading flames.

The fire burned throughout the morning as police secured the area as a crime scene.

Police SWAT teams were forced to evacuate 33 nearby residents in an armoured personel carrier.

The dead volunteer firefighters were identified as Lt. Michael Chiapperini and Tomasz Kaczowka, according to Michelle Hook, the attorney general's spokeswoman.

The injured firefighters were identified as Joseph Hofsetter and Theodore Scardino, and the off-duty police officer was identified as John Ritter.

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