New York, Jan 21 (IANS): A New York Army National Guard helicopter crashed while on a routine training mission, state Governor Andrew Cuomo said in a statement on Thursday.

"Tonight we are devastated by the crash of a New York Army National Guard helicopter in the town of Mendon that killed three of New York's bravest during a training mission," Xinhua news agency quoted Cuomo as saying in the statement.

"I'm directing that flags on all State buildings be lowered to half-staff tomorrow.

"National Guard members are our citizen soldiers who voluntarily serve and protect both here and aboard, and I extend prayers and condolences from all New Yorkers to the family, loved ones and fellow soldiers of these honourable heroes who we will never forget," the Mayor added.

The UH-60 medical evacuation helicopter was based at the Army Aviation Support Facility at Rochester International Airport, according to the National Guard.

The helicopter crashed in an open field on Wednesday evening, ABC News quoted the Monroe County Sheriff's Office as saying.

According to 911 calls, the aircraft was flying very low and there were reports of engine sputtering, authorities said during a press briefing on Wednesday night.

The aircraft was engulfed in flames when first responders arrived, they added.

The New York National Guard and Federal Aviation Administration are conducting an investigation to determine the cause of the accident.