Iran struck Gulf infrastructure Sunday, hitting fuel tanks at Kuwait’s airport and a desalination plant in Bahrain, with at least four reported dead in the region as Tehran pressed its campaign there into a second week.

In Saudi Arabia, the civil defence said a “military projectile” killed two people—an Indian and a Bangladeshi—and injured 12 others after it fell in a residential area in Al-Kharj governorate south of Riyadh.

In Kuwait, two border guards were killed “while performing their national duty”, the interior ministry said, without elaborating on the circumstances.

Gulf countries have borne much of Tehran’s response after the US and Israel launched a massive air campaign against Iran, with 18 people, 10 of them civilians, killed in the Gulf states since the war began, according to an AFP tally.

Iran’s President Masoud Pezeshkian warned Sunday that the Islamic Republic “will be forced to respond” against its neighbours if their territory was used to attack it.

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

Gulf countries have said their territory has not been used in attacks against Iran, and before the war began they repeatedly said they would not allow such a move.

Saudi Arabia, the United Arab Emirates, Qatar and Kuwait all reported new attacks on Sunday.

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.”