Iran's Islamic Revolutionary Guard Corps (IRGC) launched ballistic missiles and drones at US bases in Kuwait and Bahrain early on June 28, in retaliation for fresh US strikes on Iran's southern coast, in the most serious breakdown of the ceasefire since the war ended, state media reported.

The exchange pushes the fragile 60-day process meant to secure a permanent peace to the brink of collapse, with each side accusing the other of violating the Islamabad memorandum barely two weeks after it was signed, and the dispute centred on control of the Strait of Hormuz.

The IRGC said it had struck eight key pieces of infrastructure at the Ali al-Salem base in Kuwait and the Fifth Fleet at Port Salman in Bahrain.

US Central Command said its fighter jets had struck 10 Iranian military targets in and near the Strait of Hormuz, including military equipment, communication systems, air defence sites and drone storage facilities, in direct response to continued aggression against commercial shipping. It said Iran had been given a chance to honour the ceasefire but had instead launched a one-way attack drone that hit a Panama-flagged tanker.

The IRGC said the United States had attacked five coastal posts in Iran under what it called the pretext of the IRGC Navy confronting an offending ship, and that its forces had destroyed the targets in Kuwait and Bahrain in response.

A US official told US-based Reuters there were no reported US casualties or major damage to US facilities in the region, an account at odds with the IRGC's claim to have destroyed the sites.

The IRGC said that under the memorandum, arrangements for controlling passage through the Strait of Hormuz rested with Iran, and that offending ships would be dealt with more forcefully than in the past.

Any enemy aggression, under any pretext, even against minor targets, would draw a crushing response, it said, warning that violating the ceasefire would lead to a complete halt to the process.

Iran's foreign ministry condemned what it called brutal US attacks and a violation of the ceasefire, saying they showed the United States placed no value on its commitments.

The clash followed a drone attack on a vessel in the Strait of Hormuz the previous day, after which the United States struck Iranian coastal sites, and Iran said its navy had responded against US military targets.

The Islamabad memorandum, signed on June 17, set a 60-day window for a permanent deal and committed Iran to allow commercial vessels to pass through the strait.