United Nations, June 4 : UN Secretary-General Antonio Guterres is alarmed by the reported exchange of fire overnight between the United States and Iran and by reports that Iran has targeted Kuwait and Bahrain, his spokesperson has said.

The UN chief "is deeply troubled by reports of civilian casualties," spokesperson Stephane Dujarric told a daily briefing on Wednesday (local time).

"The Secretary-General calls on all parties to exercise maximum restraint and to avoid any further escalation that risks undermining ongoing diplomatic efforts," said Dujarric, stressing that the sovereignty and territorial integrity of all countries must be fully respected.

He said the secretary-general condemns all attacks on civilian infrastructure and recalls that international humanitarian law strictly prohibits the targeting of civilian objects, and calls on all parties to uphold their obligations under international law and to take all feasible precautions to protect civilians, reports Xinhua news agency.

"The Secretary-General reaffirms his full support for all ongoing mediation efforts, including those led by Pakistan, and urges all parties to engage constructively and in good faith with diplomatic initiatives," said the spokesperson.

Meanwhile, Iran's Islamic Revolutionary Guard Corps (IRGC) said on Wednesday its navy had targeted a US destroyer in the Gulf of Oman that sought to approach Iranian territorial waters.

In a statement published by its official outlet, Sepah News, the IRGC said its navy tracked US "aggressive actions, violations of the regulations of the Strait of Hormuz and malicious acts against Iranian commercial vessels in the Gulf of Oman," identified the command centre aboard a US destroyer, and struck it.

The IRGC said its navy is closely watching US and Israeli "enemies" and will respond instantly to any hostile move.

The US Central Command later denied the claim on the social media platform X, saying US military assets at sea continue to operate "safely and unimpeded."

Separately, the IRGC denied firing any missile or drone at a passenger terminal at Kuwait International Airport, saying the damage to the terminal was caused by a malfunctioning US Patriot missile system, according to Sepah News.

Earlier on Wednesday, Kuwaiti authorities said one person was killed, and dozens of others were injured after ballistic missiles and drones struck civilian and vital facilities across the country, including the airport, in attacks they attributed to Iran. Meanwhile, the IRGC confirmed launching missile and drone attacks on US bases in Kuwait and Bahrain.

Iran tightened its grip on the Strait of Hormuz beginning February 28, when it barred safe passage of vessels belonging to or affiliated with Israel and the United States following their joint strikes on Iranian territory.

The United States has also imposed a naval blockade on the strait, preventing ships travelling to and from Iranian ports from transiting the waterway.

The latest developments came as Iran and the United States have, over the past weeks, reportedly exchanged several proposed plans outlining conditions for peace through Pakistan's mediation, and are working to finalise a memorandum of understanding aimed at ending the war.

/IANS