The Saudi man who blew himself up inside a Shia mosque in Kuwait last week, killing 27 worshippers and wounding more than 200, had no background suggesting he planned to carry out a terrorist attack, according to officials.
The details released by Saudi and Bahraini authorities paint a fuller picture of the suicide bomber behind Friday's attack, which targeted one of Kuwait City's most prominent Shia mosques.
A branch of the Islamic State (IS) group claimed responsibility for the bombing.
The blast - which struck within hours of deadly attacks in Tunisia and France - has rattled largely stable Kuwait. The small, oil-rich country, ruled by a Sunni monarchy and with a sizable Shia minority, has mostly avoided the sectarian violence rocking other parts of the region.
Kuwaiti officials have identified the bomber as Fahad Suleiman Abdulmohsen al-Gabbaa, a Saudi man in his early twenties who landed in the country just hours before the attack, having passed through Bahrain.
Bahrain's interior ministry said al-Gabbaa arrived in the island nation on a Gulf Air flight from the Saudi capital, Riyadh, on Thursday night. He remained in transit for two and a half hours before boarding a connecting flight to Kuwait.
Saudi Arabia's interior ministry said the bomber had no record with security forces or any background indicating terrorist activities. It confirmed he left the kingdom on Thursday bound for Bahrain.
An audio message accompanied by two still photos that was posted online and promoted by Twitter accounts affiliated with IS purports to be a final message from al-Gabbaa.
A caption below the clip calls the bomber a "soldier of the caliphate" and identifies him by the nom de guerre of Abu Suleiman al-Muwahhed.
In the message, the speaker vows to pursue jihad against his enemies, particularly Shias in Kuwait, saying "we are on the lookout for you."
He also addresses IS leader Abu Bakr al-Baghdadi, telling him to "be patient and swear to God that we are with you".
IS militants consider Shias to be heretics and are fighting Iranian-backed Shia militias in Iraq and Syria.
The group's Najd Province offshoot, which said it was behind the Kuwait mosque attack, has claimed it was behind two attacks on Shia mosques in Saudi Arabia in late May. The branch's name refers to the central region of Saudi Arabia.