Venezuelan President Nicolas Maduro accused political foes of trying to kill him during an open-air speech Saturday using explosives-laden drones, prompting a host of questions about the alleged attack and who might have been behind it.

Wherever the investigation leads, Maduro's allegations raised the specter of unmanned aerial vehicles being used by militant groups or others to launch bombing, chemical or biological attacks, a tactic that has long worried security experts.

The market for commercial drones has flourished in recent years amid widespread availability and falling prices.