Social media users who use tweets and online posts to comment on a military operation could be regarded as legitimate military targets.

Australian army Land Warfare Studies Centre analyst Chloe Diggins on Thursday said a recent social media war between Israel and Hamas raised complex ethical questions about who was a combatant and therefore a legitimate military target.

A key question was whether such comments constituted an act of war.

"If that's the case, this might mean that those using social media in support of military operations are now legitimate targets," she wrote in a blog for the Australian Strategic Policy Institute.

The Geneva Convention defines legitimate military targets as objects "which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralisation, in the circumstances ruling at the time, offers a definite military advantage".