Troops on the battlefield could soon face a new threat — swarms of autonomous kamikaze drones loaded with explosives.

That is the assessment of a leading Australian military thinker after claims "killer drones" were both deployed and defused over recent days in the Middle East.

Iran is accused of preparing to launch a squadron of drones, while Israel has been blamed after one exploded in Lebanon's capital.

What are these things?

Pilot-free aircraft have been used in conflict for decades.

Missiles have been launched from the land, sky and sea for even longer.

Now, so-called suicide drones are combining these capabilities.

They can lurk in the skies for hours — waiting for their target to emerge — before dive-bombing at close to 200 kilometres per hour and detonating.

Are we talking about drones you can buy at the shop?

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 40 seconds 40 s Hezbollah leader vows to shoot down Israeli drones

Sometimes.

The New York Times previously reported on Islamic State in Iraq attaching explosives to off-the-shelf products.

By contrast, a drone used by the United States military was estimated in 2017 to cost $US70,000 ($103,000).

It is unclear exactly what equipment was in play over recent days.

But an image of one of the Beirut drones, released by Lebanese state media, showed a quadcopter-style device.

An image of one of the Beirut drones released by Lebanese state media. ( Supplied )

How dangerous can they be?

The technology has the potential to cause major problems for militaries.

Defence capability expert Malcolm Davis said "a swarm of these drones" could attack a target "like a swarm of insects".

They could strike without the adversary "really having much of a chance to stop them," he told the ABC.

"Potentially hundreds of these things coming in reasonably high speed, at low levels, [are] virtually impossible to detect on radar," Dr Davis said.

Israel has accused Iranian forces and militias of planning "killer drone attacks" from within Syria. ( Iranian Defence Ministry via AP )

The manufacturers of top-end kamikaze drones say the weapons are highly accurate and usually strike within a metre of the target.

What happened with these 'killer drones' in Lebanon and Syria recently?

Israel over the weekend claimed credit for an air strike against Iranian forces and militias it accused of planning "killer drone attacks" from within Syria.

Israel said "a number of attack drones" each loaded with several kilograms of explosives were set to be launched.

Its defence force released video purporting to show operatives transporting one of the devices near the launch site.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 21 seconds 21 s Footage said to show "killer drone"

The Syrian Observatory for Human Right said five people were killed.

Separately, Hezbollah blamed Israel after two drones came down in the Lebanese capital Beirut.

The group claimed one "killer drone" exploded and caused damage to its media centre.

What do these latest drone attacks mean?

Broken windows are seen on the 11-floor building that houses the media office in a stronghold of the Lebanese Hezbollah group in a southern suburb of Beirut.

Tensions were already rising in the Middle East and both Israel and Iranian-backed Hezbollah traded strong rhetoric after these events.

Hezbollah's Hassan Nasrallah said the drone incursions marked "the first clear, big, dangerous, breach of the rules of engagement" drawn up after a 2006 war between the two sides. He flagged an imminent response.

But a former head of Israeli military intelligence, Amos Yadlin, said neither Iran nor Israel wanted all-out war.

"But sometimes, someone makes a mistake," news agency Reuters quoted him as saying.

Could we see more of these kamikaze bombers in conflicts?

Could a drone this small kill? ( Reuters: Benoit Tessier - file photo )

You bet, especially since the technology has developed significantly over the past decade.

Malcolm Davis, of the Australian Strategic Policy Institute, warned the Australian Defence Force (ADF) needed to be prepared.

"If the ADF is deployed operationally, they should expect attacks by masses of swarming drones that can operate autonomously and self-coordinate."

That's right — Dr Davis said self-directed suicide drones were becoming a real prospect for modern conflicts.

"They have their course programmed in before launch, then they fly that course towards a target, and then they coordinate amongst themselves in a swarm to attack a target," he said.

"Attacking it like a swarm of bees, except each bee has a high-explosive charge in it.

"When you're talking about large swarms of hundreds or even thousands of drones, it becomes very difficult to stop that."

Fortunately for Australian troops, he said the defence force was "very aware" of the threat.