Live updates: Fuel excise halved and heavy vehicle road user tax halted for three months; Iran 'preparing for ground invasion'; UN peacekeeper killed

On home soil, Australians heard some major announcements from both federal and state leaders on securing our fuel supply, while overseas, the landing of fresh ground troops cast a shadow over peace talks and Human Rights Watch accused Iran of potential war crimes.

Here are today's key events so far:

- Following this morning's meeting of National Cabinet, the prime minister announced a four-level National Fuel Security Plan, which amounts to a staggered approach to reducing fuel use and securing supplies, culminating in fuel rationing at 'level four';

- The price of unleaded fuel has hit $2.53 a litre nationally. To address soaring prices, the government will halve the fuel excise for three months from April 1, slashing 26.3 cents a litre off the price of fuel;

- Trucks and buses will also receive relief with the temporary halting of the heavy vehicle road user tax. Combined, the measures will cost taxpayers $2.55 billion;

- Overseas, 2500 US Marines have landed in the Middle East ready to join the conflict and Israel launched a fresh round of strikes on Tehran using 150 fighter jets;

- Human Rights Watch has accused Iran of violating the rules of warfare by repeatedly using illegal cluster munitions in strikes on Israel.

The average cost of unleaded petrol at bowsers across Australia has exceeded $2.50 a litre for the first time ever.

According to the latest report from the Australian Institute of Petroleum, unleaded petrol prices have averaged $2.534 a litre in the last seven days.

That's just over 15 cents more than a week ago, when it was $2.38 a litre.

However, relief is in sight as the federal government is set to halve the fuel excise from Wednesday in a move announced earlier today, which is expected to slash 26.3 cents a litre off the price of fuel.

Energy Minister Chris Bowen has provided parliament with an updated report on Australia's current fuel reserves.

As of today, we have:

• 39 days' supply of unleaded petrol
• 30 days' supply of diesel
• 30 days' worth of jet fuel

Bowen said that importers and refiners are delivering petrol into regional Australia at "record levels".

A new report just released by not-for-profit Human Rights Watch claims Iran has repeatedly used unlawful cluster munitions in its strikes on Israel.

At least four civilians have been killed by the inherently indiscriminate munitions, delivered by ballistic missiles sent from Iran, according to Human Rights Watch.

In one attack, two men in Yehud near Tel Aviv were killed on March 9.

In a second, an elderly man and woman were killed in Ramat Gan on March 18.

Human Rights Watch says using the munitions violates the rules of warfare and may amount to war crimes.

Cluster munitions are fired in rockets, missiles and projectiles or dropped from aircraft and then typically disperse in the air, spreading dozens of explosive "bomblets" indiscriminately over a large area.

Many fail to explode on initial impact, leaving duds that can kill and maim, like landmines, for years or even decades unless cleared.

The 2008 Convention on Cluster Munitions - which Iran has not joined - bans all development and use of cluster munitions.

Human Rights Watch says it has written to the Iranian government regarding the use of cluster munitions, but has not received a response.

Iran has responded to reports the US is planning a secret ground invasion with fresh threats.

Iranian forces "are waiting for the arrival of American troops on the ground to set them on fire and punish their regional partners forever," parliamentary speaker Mohammad Bagher Qalibaf said.

"Our firing continues. Our missiles are in place. Our determination and faith have increased."

The renewed threats come even as regional powers are meeting in Pakistan to discuss how to end the fighting.

About 2500 US Marines have arrived in the Middle East, and Iranian-backed Houthi rebels have also entered the fray.

The federal government has released the full version of its National Fuel Security Plan, which was agreed to at a meeting of National Cabinet today.

The plan outlines four levels of action taken by federal and state governments in response to "an unprecedented shock to global oil and gas supply".

Australia's current status is "level two".

You can find it here.

Chris Minns said forgoing additional GST revenue from elevated prices is on the table across all the states.

"The states are considering forgoing any win for GST revenue due to prices being elevated and extremely high," Minns said.

"All my colleagues across the states have indicated that that is appropriate.

"Nobody wants to profit while people are doing it so tough, particularly across the Easter period."

Such a scheme would involve taking the additional GST directly off the sticker price of relevant goods, Minns said.

The Goods and Services Tax (GST) accounts for almost a quarter of the states' revenue, totaling more than $100 billion nationally.

NSW Premier Chris Minns has confirmed the government is preparing for a prolonged conflict in the Middle East, directly contradicting US President Donald Trump's repeated claims of a swift victory.

"I am not seeing any indication that this will be resolved in 30 days," Minns said.

"I don't know whether it is going to be over in a week, or whether it's going to be a prolonged situation... but we have got to prepare for every eventuality."

The prime minister has concluded his press conference.

We turn now to NSW Premier Chris Minns, who has welcomed the federal and state governments' agreed-upon national fuel plan.

Minns said stages three and four of the fuel plan will only come into effect if there are lengthy disruptions coming out of the Middle East conflict.

"We are not necessarily sure what will happen in the Middle East in the next three or six months," he said.

"We are not making a decision today to tell people to cancel their trips around the state or cancel Easter holidays.

"But as time goes on, we may tell people to use their common sense on this and reduce their usage."

While Prime Minister Anthony Albanese said that while he supported regime change in Iran, he would like more clarity on US President Donald Trump's plans in the region.

"I want to see more certainty in what the objectives of the war are, and I want to see a de-escalation," Albanese said.

"A de-escalation is in the global economy's interests."