"The Royal Oman Police have responded to a shooting incident that occurred in the vicinity of a mosque in the Al-Wadi Al-Kabir area," local police said in a statement, according to Lebanese Al Mayadeen English news website.
The authorities initially reported that four people were killed and "several others" wounded at the mosque in eastern Muscat.
"The authorities are continuing to gather evidence and conduct investigations to uncover the circumstances surrounding the incident," it added.
A voice is heard saying "Oh God" and repeatedly mentioning "Oh Hussein," referring to Imam Hussain ibn Ali, the grandson of Prophet Muhammad.
According to Reuters, the terror attack targeted Shia Muslims in Oman who were marking Muharram, the martyrdom anniversary of third Shia Imam, Imam Hussein and his companions in the battle of Karbala.
It is worth noting that Muslims from around the world are commemorating the martyrdom of Imam Hussein ibn Ali, the grandson of Prophet Muhammad, at the Battle of Karbala in the year 61 AH (AD 680) this week.
MNA