The United States and Iran have exchanged fire in the Strait of Hormuz, prompting fears that the already fragile ceasefire between the warring nations could collapse.

The flare-up in fighting on Thursday came as Washington awaits a response from Tehran to its latest proposals for an agreement to end the war, which began with joint US-Israeli air strikes on Iran on February 28.

Here’s what we know about how significant the latest clashes are and what each side is trying to achieve.

What happened in the Gulf on Thursday?

US President Donald Trump said three US Navy destroyers were attacked as they moved through the Strait of Hormuz, a conduit through which one-fifth of the world’s oil and liquefied natural gas (LNG) supplies are shipped during peacetime, but which Iran has all but closed since the conflict started. Last month, the US launched a naval blockade of Iranian ports in return.

“Three World Class American Destroyers just transited, very successfully, out of the Strait of Hormuz, under fire. There was no damage done to the three Destroyers, but great damage done to the Iranian attackers,” Trump wrote on Truth Social.

Trump later told reporters that the ceasefire, which began in early April between the US and Iran, was still in effect and sought to play down the exchange.

“They trifled with us today. We blew them away,” Trump said in Washington.

But Iran’s top joint military command accused the US of violating the ceasefire by targeting an Iranian oil tanker and another ship. It also said the US carried out air attacks on civilian areas on Qeshm Island, a strategic point at the entrance to the Strait of Hormuz believed to house much of Iran’s naval force, and nearby coastal areas in Bandar Khamir and Sirik in southern Iran. Iranian air defences were also triggered over western Tehran. The military said it had responded to these incidents by striking US military vessels east of the strait and south of the port of Chabahar.

A spokesperson for Iran’s Khatam al-Anbiya Central Headquarters, the operational base of Iran’s Armed Forces, claimed the Iranian strikes inflicted “significant damage”, contrasting with the US Central Command claim that none of its assets had been hit.

Iran’s Press TV later reported that, following several hours of fire, “the situation on Iranian islands and coastal cities by the Strait of Hormuz is back to normal now”.

It remains unclear which side started Thursday’s clashes but the two sides have occasionally exchanged gunfire since the ceasefire took effect on April 8, with Iran hitting targets in Gulf countries, including the United Arab Emirates.

On Friday, the UAE Ministry of Defence said that “the audible blasts reported throughout the nation stem from active operations to intercept and engage incoming missiles and drones coming from Iran”. Since the war began, Iran has frequently targeted US military assets and infrastructure in neighbouring Gulf countries, with the UAE taking the largest share of hits.

Earlier this week, the UAE said Iranian missiles had been fired at the port in its Fujairah emirate, where an oil refinery caught fire.

How significant are the latest clashes?

A ceasefire between the US and Iran has been in place since April 8. While a naval standoff has been playing out in the Gulf with Tehran’s closure of the Strait of Hormuz and Washington’s blockade of Iranian ports, Thursday’s clashes appeared to mark a sharp escalation for the first time since the truce.

Former US diplomat and security specialist Donald Jensen characterised the latest naval clash in the Strait of Hormuz on Thursday as a “controlled escalation” rather than “mere skirmishes”, arguing that both nations are “trying to show their resolve” while attempting to “settle on a framework on some key issues”, referring to the diplomatic efforts to reach an agreement.

Jensen told Al Jazeera that while a resolution is likely between the two, “it’s not going to be the kind of comprehensive agreement that either side wants”, but will instead be “much more limited to focus on the passage through the strait primarily”.

He also cautioned that broader diplomatic goals, “especially regarding the nuclear programme in Iran, will have to be put aside for the time being” as the international priority shifts towards getting “the global economy back working”.

Reporting from Washington, DC, Al Jazeera’s Kimberly Halkett said US Central Command in Tampa, Florida, has insisted that Washington’s action in the strait on Thursday was a self-defence measure and noted that this statement is consistent with what US officials have been saying all week, as there has been an escalation in the Strait of Hormuz.

“Secretary of State Marco Rubio this week said that the United States will be acting in self-defence, and the US president essentially said the same thing in a Truth Social post in just the last couple of hours,” Halkett said.

“Like CENTCOM, he said the US has been very successful in the strait. They blame Iran for having to defend US interests, and what’s most interesting is there’s a real difference of opinion whether or not there is damage to US vessels,” she added.

Trita Parsi, executive vice president of the Quincy Institute for Responsible Statecraft, a US foreign policy think tank, told Al Jazeera that Iran is likely to perceive the latest attacks by the US as an effort to create in the Gulf “what Israel has created in Gaza, in the West Bank and in Lebanon, in which a ceasefire is essentially unilateral”.

Parsi noted: “If the US decides to shoot, then that is not, in and of itself, a violation of the ceasefire.”

“This situation may be more complex; there’s conflicting stories as to whether the Iranians started shooting first or not. But the idea that something like this could be done … is very difficult for the Iranians to accept,” he said.

“Whether there is a chance to go back to a ceasefire and make sure that this doesn’t escalate any further is a different story … both of them probably have an interest in making sure that this does not get out of control,” he added.

So, what does this mean for the ceasefire?

US President Donald Trump insists the ceasefire with Iran is still in effect, despite Thursday’s exchange of fire in the Strait of Hormuz. Trump has also threatened more strikes if Iran does not sign a truce quickly, however.

On Thursday, Iran said it was reviewing the latest US peace proposal.

Reporting from Tehran, Al Jazeera’s Resul Serdar Atas said the Iranians are accusing Israel and the US of violating the ceasefire, however.

“The spokesperson of the Iranian Foreign Ministry said his side is still reviewing the US proposal. There were reports that the response to the proposal was expected to be sent to Pakistani mediators yesterday,” he said.

“This has not been confirmed, but Iranian officials are saying they’re still reviewing it. So despite this back and forth and these military confrontations, the diplomatic and mediation efforts seem to be still under way, and both sides are still interested in diplomatically engaging with each other,” he added.

Ali Vaez, director of the Iran Project at the International Crisis Group, told Al Jazeera: “The US is trying to loosen Iran’s chokehold upon the Strait of Hormuz while Iran remains determined to push back.

“Both sides would either have to make painful concessions or leave the main areas of disagreement vague if they are to finalise a framework understanding,” he added.