Four people have been killed and several others wounded in a shooting near a mosque in Oman’s capital, Muscat, police say.

A brief statement issued overnight said officers had responded to the incident and were now conducting “investigations to uncover the circumstances”.

In videos posted on social media, gunfire can be heard and police seen in the vicinity of the Imam Ali mosque, where Shia Muslims had gathered to mark the start of the holy day of Ashura.

The police provided no details about the identities of the attacker and the victims, as well as the apparent motive. But Pakistan’s ambassador suggested that its citizens were among the wounded.

Imran Ali said in a video that he had visited some in three local hospitals and described their conditions as “relatively safe”.

He also advised Pakistani residents of Oman to avoid al-Wadi al-Kabir and to co-operate with local authorities.

The US embassy warned US citizens to be vigilant and cancelled visa appointments on Tuesday as a safety precaution.

Such violence is rare in Oman, a Gulf state that has long been seen as one of the most stable and secure countries in the Middle East. This has allowed it to play a leading role in mediation efforts to try to resolve conflicts and disputes in the region.

The sultanate has a population of about 4.6 million, of which more than 40% are foreign workers.

The government does not publish statistics about religious affiliation.

However, the US state department estimates that 95% of the population is Muslim, with 45% Sunni, 45% Ibadi and 5% Shia. Hindus, Buddhists and Christians make up the remaining 5%.