Two Venezuelan military personnel were killed and two others injured Tuesday when a Russian-made helicopter crashed in the South American nation, President Nicolas Maduro said.

"Today we have had a sad and regrettable accident in the state of Lara, with an Mi-17 helicopter with two fatalities and two pilots who are fighting for their lives," Maduro said during a meeting with ministers broadcast on state television.

It was unclear why the chopper went down, and Maduro has ordered an investigation. 

The aircraft burst into flames when it crashed, and the injured pilot and co-pilot were pulled to safety by local residents and laborers.

The Venezuelan army said in a statement that the crash occurred during "a supply mission to border protection bases."