At least nine people were killed and about two dozen were wounded in violent clashes with police and paramilitary forces on Sunday after hundreds of protesters stormed the US Consulate in the Pakistani port city of Karachi, authorities said.

The violence came hours after the United States and Israel attacked Iran and killed the country’s supreme leader, Ayatollah Ali Khamenei.

Police and officials at a hospital in Karachi said at least 25 people were wounded in the clashes and some of them were in critical condition.

Summaiya Syed Tariq, a police surgeon at the city's main government hospital, confirmed that initially six bodies and multiple injured people were brought to the facility. However, she said the death toll rose to nine after three critically wounded died.

The US Embassy in Pakistan wrote on X that it was monitoring reports of ongoing demonstrations at the US Consulates General in Karachi and Lahore, as well as calls for additional protests at the US Embassy in Islamabad and the Consulate General in Peshawar.

It advised US citizens in Pakistan to monitor local news, stay aware of their surroundings, avoid large crowds and keep their travel registration with the US government up to date.

Karachi is the capital of southern Sindh province and Pakistan’s largest city.

Senior police official Irfan Baloch said protesters briefly attacked the perimeter of the US Consulate but were later dispersed.

He dismissed as baseless reports that any part of the consulate building was set on fire. However, he said protesters torched a nearby police post and smashed windows of the consulate before security forces arrived and regained control.

Witnesses said dozens of Shi'ite protesters remained gathered about a kilometre from the consulate, urging others to join them.

They said one of the protesters had tried to burn a window of the consulate before security forces arrived there and dispersed the demonstrators.

It prompted Pakistan's Interior Minister Mohsin Naqvi to issue an appeal for calm.

In a statement, he said, “Following the martyrdom of Ayatollah Khamenei, every citizen of Pakistan shares in the grief of the people of Iran.”

He described it as “a day of mourning for the Muslim Ummah and for the people of both Iran and Pakistan,” but urged people not to take the law into their own hands and to express their protests peacefully.

Shi'ites also held a peaceful rally in Multan, a city in Punjab province, chanting slogans against Israel and the United States.

Mamoona Sherazi, who attended the rally, said she was protesting the killing of Iran’s Supreme Leader.

She described Khamenei as a fatherly figure and a strong voice for Shi'ites, adding that he also supported Sunni Muslims facing oppression. “God willing, we will never bow before America and Israel,” she said.

Shi'ites also held a rally near the US Consulate in Lahore, the capital of eastern Punjab province, police said. (AP)