The attack occurred just after Maghrib early evening prayers at the Al-Mashad mosque in the southern city's Dahza neighbourhood, said the Saudi interior ministry.
The IS jihadist group claimed responsibility for the attack on what it said was an Ismaili Shiite mosque, said SITE Intelligence Group, a US monitoring organisation.
Al-Hijaz Province, a group affiliated to IS, said on Twitter that a fighter named Abu Ishaq al-Hijazi detonated his explosive belt at the mosque, causing "many" casualties.
In August, the same group claimed another blast in Saudi Arabia's southern region. Fifteen people died in that suicide bombing at a mosque frequented by members of a police special weapons and tactics unit in Abha city.
"As worshippers were leaving the mosque, a person wearing a suicide belt entered and blew himself up amongst them," the ministry said of the latest attack.
It said one person was killed at the scene and a second died later of injuries. The wounded were taken to hospital, it said without giving a number.
On its Twitter account, the ministry said investigators found a vehicle belonging to the bomber.
The vehicle contained a letter to his parents about his crime, the ministry added.
Neither the ministry nor the television specified whether the mosque belonged to the kingdom's Sunni majority or the Shiite minority.
But roughly half of Najran's population belongs to the Ismaili community.
Most of Saudi Arabia's Shiites live in Eastern Province, where they have been targeted four times in the past year by bombings and shootings linked to the IS group of Sunni extremists, who consider them heretics.
Ashura is one of the holiest occasions for the Shiite faith.
In June, four Shiites died preventing a suicide bomber from entering the hall of Al-Anoud mosque in Dammam city.
Days earlier, 21 people were killed in another Shiite mosque bombing in Eastern Province.
Groups claiming affiliation with IS said they carried out the earlier blasts and the Ashura shooting.
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
