Two border guards were also killed "while performing their national duty", Kuwait's interior ministry said without elaborating on the circumstances.

Neighbouring countries have borne much of Tehran's response after the US and Israel launched a massive air campaign against Iran, with 16 people, eight of them civilians, killed in the Gulf states since the war began, according to an AFP tally.

Iran President Massoud Pezeshkian warned Sunday that the Islamic republic "will be forced to respond" against neighbouring countries if their territory is used to attack it.

On Saturday the president had apologised to neighbouring countries hosting US military bases for attacks on their territory.

Saudi Arabia, the United Arab Emirates, Qatar and Kuwait all reported new attacks, after loud explosions were heard in Dubai and Bahrain's Manama a day earlier.

Fuel tanks at Kuwait's international airport were targeted in a drone attack, the military said.

The official Kuwait News Agency said a fire at the airport was brought under control, reporting no "significant injuries".

The military called the drone attack "a direct targeting of vital infrastructure".

A separate statement said "some civilian facilities sustained material damage as a result of falling fragments and debris from interception operations".

- 'Drone threats' -

Kuwait's national oil company announced a "precautionary" cut to its crude production, as the country's military said Sunday that it had responded to several drone and missile attacks.

Authorities said Kuwait's main building for social security was targeted, causing material damage, and that it would not receive visitors there on Sunday.

Bahrain's interior ministry said Sunday that an Iranian drone attack damaged a water desalination plant, accusing Tehran of "randomly" targeting civilian infrastructure.

Iran's Revolutionary Guards Corps said on Saturday that it had struck the United States' Juffair base in Bahrain, adding it had been used to attack an Iranian desalination plant earlier in the day.

Bahrain's national communication office later said the Iranian attack on a water desalination facility has had no impact on water supplies or network capacity.

Falling missile debris also injured three people and damaged a university building in the Muharraq area, the interior ministry said in a separate statement.

Saudi Arabia's defence ministry said on Sunday that it intercepted 33 drones, adding there were no reports of damage or casualties from the attacks.

Among them was a drone targeting Riyadh's diplomatic quarter, thwarted with no material damage or civilian injuries, the ministry's spokesman said, adding the capital and surrounding areas were targeted by 26 drones.

One drone targeted the Shaybah oil field in the southeast of the country, according to the Saudi defence ministry.

- 'At the disposal of the enemy' -

The UAE said its air defences were responding to "incoming missile and drone threats from Iran", while Qatar said 10 ballistic missiles and two cruise missiles fired from Iran the previous day were mostly intercepted without casualties.

Despite the Iranian president's apology to the Gulf countries for earlier strikes, hours later its judiciary chief said strikes would continue on sites in Gulf countries that were "at the disposal of the enemy".

UAE President Mohammed bin Zayed Al Nahyan said in a rare televised address that the Emirates were in "a period of war" and "will emerge stronger" from it.

Dubai authorities said Saturday that a Pakistani national had been killed by debris from an "aerial interception".

Dubai briefly closed its main airport -- the world's busiest for international traffic -- on Saturday after authorities said an unidentified object was intercepted nearby.

A witness told AFP of a loud explosion in the area followed by a cloud of smoke. Footage verified by AFP recorded the sound of a drone followed by a loud explosion and plumes of smoke close to an airport concourse.

The government said there had been "a minor incident resulting from the fall of debris after an interception", without directly mentioning the airport. It said there were no injuries.