Police were called to the scene at 11:43 local time, and "observed what appeared to be three deceased victims out front", the police chief says.

More officers arrived within four minutes, he continues.

"At about the same time, we began to receive calls from a couple blocks away of more active gunfire."

Officers quickly responded to both scenes, he says.

San Diego Police Chief Scott Wahl is speaking to the media.

He says there is no further threat in the area and two suspects are "deceased".

The police chief adds that there are three adults who died at the Islamic Center.

"Our hearts go out to the families that are in this moment being notified of what has happened to their loved ones," he says.

In the next few minutes we are expecting a statement from San Diego police on the incident.

You can watch live at the top of this page.

Sareen Habeshian
Reporting from California

Sharp Memorial Hospital is receiving patients related to the shooting, a spokesperson for Sharp HealthCare tells the BBC.

"Reports indicate multiple injured people," spokesperson Alicia Cook says.

"Our disaster procedures have been activated and we are coordinating with the County of San Diego and other resources to respond to the incident," Cook adds.

San Diego Mayor Todd Gloria says the city's police department has advised that there is no ongoing threat to the community.

In a social media post, Gloria thanks emergency services and law enforcement "who responded quickly to protect lives and secure the area".

Witnesses are continuing to describe their experience to CBS, the BBC's US partner.

One woman speaking with CBS says her grandchildren were in the nearby Hebrew school, which also went into lockdown when the shooting happened.

The children are 11 and 13, says the woman. The Hebrew school is located across the street from the Islamic Center of San Diego.

Her granddaughter has been able to text her, sending a message from lockdown saying: "I think we're safe."

Aerial video from the scene showed children holding hands and being escorted through a parking lot of the Islamic Center, which has a school on its campus.

Nearby schools were also placed on lockdown as police responded to the area.

A reunification location was established for parents to meet their children.

Image source, Reuters

The Islamic Center is the largest mosque in San Diego County, with more than 5,000 members in its congregation, according to its website.

The campus includes the Al Rashid School, which offers religion and language courses.

According to its website, the centre's mission is to serve the Muslim population, and also "work with the larger community to serve the less fortunate, to educate, and to better our nation".

A witness speaking to CBS News, the BBC's US partner, says he heard up to 30 gunshots from what sounded like "a semi-automatic weapon".

He said he first heard about a dozen shots, then a pause, then another possibly dozen shots.

The man, who is retired and was eating lunch at home, says he called 911 and that police arrived within "five to 10 minutes".

The mosque gets very busy during holidays, he says.

"It's a good thing it didn't happen on a Friday. Because the streets would be full of people," he says.

San Diego Mayor Todd Gloria said he was "aware of the active shooter situation" at the Islamic center.

"Emergency personnel are on scene and actively working to protect the community and secure the area," he added in a social media post shared around noon local time.

California Governor Gavin Newsom's office said he has been briefed on an "evolving situation".

The Governor’s Office of Emergency Services is coordinating with local law enforcement, they said.

"We are grateful to the first responders on the scene working to protect the community and urge everyone to follow guidance from local authorities," Newsom's office said.

San Diego police say "the threat at the Islamic center has been neutralised", after reports of an active shooter in the US city.

The incident took place at the Islamic Center of San Diego in the city's Clairemont area.