Seven people shot dead at Oikos University in Oakland, California. Reuters

Seven people have been killed and at least three more injured in a shooting at a private university in Oakland, California.

Police said a suspect had been detained after the attack, which happened just after 10.30am local time on Monday at Oikos University. He was named as One Goh, 43, and described as a former student at the college.

Local media reports said the incident began when a man opened fire at Oikos, a Korean religious college offering studies in theology, music, nursing, and Asian medicine.

Oakland police spokeswoman Johnna Watson said a gunman entered the college and fired multiple shots. "I can confirm that we do have one person who has been detained that we believe is possibly responsible for this shooting," Watson said.

Emergency crews treated some of the wounded at the scene, while others were taken away by ambulances. Pictures showed at least four of the dead had been covered with tarps on an area of grass near the building.

"We're still evacuating the interior of the school. Our first priority is to evacuate the injured. Right now the Swat team is searching the school," she said.

The death toll reached six, according to city council president Larry Reid, who said he was told the count by the police chief. Shortly afterwards a total of seven dead was confirmed. Officials from a nearby hospital said they were treating a number of people from the shooting.

Watson said: "We are interviewing the witnesses right now to try to determine if this person is known to them."

A spokeswoman for Highland hospital said it had received five casualties.

Footage broadcast by the local ABC affiliate showed wounded people being brought out of the building, and more gurneys being taken in. The footage also showed bloodied victims on stretchers being loaded into ambulances.

Officers surrounded the building and a specialist Swat team went through it room by room. The suspect had been described to them as a Korean man in his 40s with a heavy build and wearing khaki clothing.

"One of the people who was inside the building, she was saying there is a crazy guy inside," witness Brian Snow told KGO-TV. "She did say someone got shot in the chest right next to her before she got taken off in an ambulance."

Offices of a local newspaper, the Oakland Tribune, were locked down during the incident. After the lockdown was lifted, the paper updated a report on its website to quote Jong Kim, a pastor who founded the school about 10 years ago, as saying he heard about 30 shots. "I stayed in my office," he said, imitating the sound of rapid gunfire.

A man who works in the IT department of the superior court of California, whose offices are near the scene, added, "A few people inside [our building] heard shots, and then there was a huge crowd outside."

Several local media reports said that the suspect was detained nearby in the Alameda city. The area was cordoned off with yellow police tape.

An English teacher at the school, Lucas Garcia, 33, told the San Francisco Chronicle he heard shots down the hall from the room where he was teaching. "I looked outside the door and someone said, 'Somebody has a gun,'" Garcia said. "So I evacuated the classroom."

Angie Johnson, 52, told the Chronicle that she saw a young woman leave the building with blood coming from her arm and crying: "I've been shot. I've been shot."

The injured woman said the gunman was a man in her nursing class who got up and shot one person at point-blank range in the chest before spraying the room with bullets, Johnson said.

The Oakland tragedy comes just over a month after a student in Ohio opened fire in a high school cafeteria, killing three students in the deadliest shooting incident at a US high school in six years.

• This article was corrected on 3 April 2012 because the original that the suspect was detained nearby in the Alameda district, when it should have said Alameda city.