Monday’s shooting killed at least six people – four Pakistanis, an Indian and an Omani police officer – and wounded 28, authorities have said.

It was the first known operation claimed by the IS group in the sultanate which is among the most stable countries in the Middle East.

“The three perpetrators involved in the incident were Omani nationals and brothers,” Omani police said in a statement on social media platform X.

“They were killed due to their insistence on resisting security personnel,” the statement said, adding that the attackers “were influenced by misguided ideas”.

In a statement Tuesday, IS’s Aamaq propaganda arm claimed the attack, saying it targeted “Shi’ites practising their annual rituals” on the occasion of the holy mourning period of Ashura

It posted a picture purporting to show the three perpetrators raising the group’s black flag.

Aamaq did not provide any details on their nationalities.

Monday’s attack came ahead of Ashura, an annual day of mourning that commemorates the seventh-century death in battle of Imam Hussein, regarded by Shi’ites as the rightful successor to the Prophet Muhammad.

IS regards Shi’ites as heretics.

Several attacks on Shi’ite mosques have roiled the Gulf in past years but this was the first in Oman.

A 2015 suicide attack on a Shi’ite mosque in Kuwait killed more than two dozen worshippers and was claimed by the IS group.

The same year, Saudi Arabia’s Eastern Province saw two attacks on Shi’ite mosques in the space of a week, with at least 25 people killed.

IS again claimed the attacks.