The shaky ceasefire between the US and Iran has been tested further, with American forces targeting Iranian drones and radar sites, and Iran firing missiles at US bases in the Gulf.
The US military said it had shot down four Iranian "one-way attack drones" launched towards the Strait of Hormuz, which it said "posed an immediate threat to regional maritime traffic".
US forces "subsequently struck Iranian coastal surveillance radar sites" in the south of the country "to defend against further attacks", US Central Command (Centcom) said.
Iran retaliated by firing ballistic missiles at two US air bases in Kuwait, and facilities of the US Navy in Bahrain, Iran's Irib news agency reported.
Centcom said initial assessments showed that of the seven Iranian missiles fired at the two Gulf states, six were intercepted and one did not reach its target.
This comes several days after the US and Iran exchanged strikes in an escalation that threatened the ceasefire that has been in place since April.
Iran's Islamic Revolution Guard Corps (IRGC) denied responsibility for the airport strike, claiming the damage was caused by an error from a US missile interceptor.
Centcom said this was false and claimed Iran struck the airport in a "deliberate, calculated and unjustified attack".
The IRGC earlier said it had targeted US bases in the Gulf in retaliation for US strikes on an Iranian oil tanker and Qeshm Island.
Even with the conflict between the two nations continuing, the US has granted visas to Iran's World Cup football team, ahead of their first match in Los Angeles on 15 June.
It is the first time the competition will see a host nation receive the team of a country it is at war with.
The attacks occurred as ceasefire negotiations between the US and Iran stalled, with a deal to end the war failing to advance, and US media reporting that President Donald Trump had requested changes to the terms of an agreement.
On Monday, Iran's foreign ministry spokesman said the US was "constantly changing its views and putting forward new or contradictory demands".
The US and Israel launched wide-ranging strikes on Iran on 28 February, sparking conflict across the Middle East.
Iran responded by attacking Israel and US-allied states in the Gulf, and effectively closing the Strait of Hormuz, through which around 20% of the world's oil and liquefied natural gas travels.
That oil comes not only from Iran, but also Gulf states such as Iraq, Kuwait, Qatar, Saudi Arabia and the UAE.
The closing of the strait sent oil prices soaring globally.
Shortly after a ceasefire was agreed in early April, the US established a blockade of Iranian ports, which Trump said would remain "in full force and effect until an agreement is reached, certified, and signed".
