Two brothers arrested in Saudi Arabia had transported the explosives used in the suicide bombing of a Shia mosque in Kuwait, the interior ministry said Tuesday.
It said Majed al-Zahrani and Mohammad al-Zahrani smuggled in the explosives in an icebox by car through Nuwaiseeb border post from Saudi Arabia, a day before the June 26 bombing that killed 26 people.
The two Saudis then delivered the explosives near the border post to Abdulrahman Sabah Eidan Saud, a stateless Arab who passed them on to the suicide bomber and drove him to the target mosque, the ministry said.
It said tests had shown that the explosives were of the same type as used in two similar attacks on Shia mosques in eastern Saudi Arabia.
In Saudi Arabia, the interior ministry said Mohammad Zahrani was arrested in Khafji, another border town near Nuwaiseeb, after a shootout with Saudi security forces.
Two security personnel were wounded in the shootout, it said, adding that brother Majed was arrested in the southwestern Saudi city of Taif.
A third brother was arrested in Kuwait and handed over to Saudi authorities, officials in the emirate said.
"Two of them were born in Kuwait and they have ties to a fourth sibling who is present in Syria as part of Daesh," the Saudi ministry said, using an Arabic acronym for the Islamic State (IS) jihadist group.
Kuwait has said more than 40 people could face charges in connection with the mosque blast.
An IS-affiliated group calling itself Najd Province claimed the Kuwait bombing and also said it carried out the two suicide attacks at Shia mosques in Saudi Arabia in May.
IS considers Shia to be heretics and has targeted them across the region.