ISLAMABAD, Pakistan - Gunmen opened fire on a political rally in the Pakistani city of Karachi on Tuesday, killing at least nine people and sparking rioting, police said.

The violence was a reminder of the port city’s volatility. It is home to several political parties with armed wings that extort its citizens and feud among themselves, leading to frequent outbreaks of violence.

City police chief Akhtar Gorchani said nine people were killed and more then 30 wounded in shootouts. Another police officer, Mohammed Amir, said the attackers fired on a rally held by Awami Tehrik, a small nationalist group, that was also attended by members of several other parties in the city.

Several cars and shops were burned following the incident.

It was unclear who the attackers were, Amir said. He said authorities were trying to restore order.

Karachi is home to 18 million people and is the commercial hub of Pakistan.

But it is divided by ethnic, political, and sectarian tensions, and is also believed to be a hiding place for Taliban and Al Qaeda militants.

The latest violence there started hours after the Pakistani Navy said it had court-martialed three officers for “negligence’’ in connection with a dramatic Taliban attack on a naval base in the southern port city of Karachi last year.

The brazen 18-hour assault on Naval Station Mehran last May destroyed two US-supplied surveillance aircraft and killed 10 people on the base.

The ability of the militants to penetrate the high-security base led to speculation they may have had inside information or assistance.