CNN  —  The jihadist ISIS group has claimed responsibility for an attack on a Shiite-Muslim mosque in the Gulf Arab state of Oman that killed six people Monday evening.

The Sunni-Muslim Islamist group said in a statement late on Tuesday that three of its “suicide attackers” fired on worshippers at the mosque and exchanged gunfire with Omani security forces until morning, Reuters reported. The group also published what it said was a video of the attack on the Telegram messaging app.

The incident has shocked a country that avoided the sectarian violence that gripped some Middle Eastern states, including some of Oman’s oil-rich neighbors, after ISIS declared a state in Iraq and Syria a decade ago and sought to expand throughout the Arabian Peninsula. The group considers Shiites heretics.

The Royal Oman Police said on Tuesday that nine people were killed in the shooting in the capital Muscat’s Wadi al-Kabir district, including the three perpetrators and a policeman. More than two dozen people of various nationalities were injured, including four Omani first responders, the police said. It didn’t identify a motive for the attack or reveal the identity of the attackers.

The attack took place at the Imam Ali mosque, according to video obtained by Reuters and geolocated by CNN, during Ashura, the 10th day of the Islamic month of Muharram, which holds particular significance for Shiite Muslims.

The oil-producing nation is one of the most stable in the Middle East and is becoming an emerging regional tourism destination as the government promotes the sector to diversify its economy away from hydrocarbons.

Unlike the rest of the Sunni-ruled Gulf states, Oman follows the Ibadi sect of Islam but has a sizable Sunni population and a small but influential Shiite minority. Religious and political leaders often emphasize sectarian harmony and religious tolerance as key to the country’s stability. About 57% of the country’s population of five million are expatriates, many of whom are Hindu or Christian.

Pakistan’s Ministry of Foreign Affairs said Tuesday that four Pakistanis were among the dead. Another 30 Pakistanis were injured and currently receiving treatment in hospital, the ministry added. It condemned the incident as a “dastardly terrorist attack.”

“We are heartened that the government of Oman has neutralized the attackers,” the ministry said.

Pakistani Prime Minister Shehbaz Sharif posted on X Tuesday that he had been “deeply saddened” by the incident.

“My heart goes out to the families of the victims. I have instructed the Pakistan Embassy in Muscat to extend all possible assistance to the injured and visit the hospitals personally,” he wrote.

One Indian citizen was killed and another injured, India’s embassy in Muscat announced in a post on X Tuesday.

The US embassy in Muscat issued a security alert for US citizens, advising them to “remain vigilant, monitor local news and heed directions of local authorities.”

It said visa appointments scheduled for Tuesday would be canceled as a safety precaution.

Oman police said military and security procedures have concluded, and an investigation is ongoing.