Police officers search a student's belongings at the University of California, Los Angeles (UCLA) campus after it was placed on lockdown following reports of a shooter in Los Angeles, California June 1, 2016. [Photo/Agencies]

Bioengineering student Bahjat Alirani said police were yelling at people to run from the scene.

"I was in Boelter Hall to take a final and I exit the staircase to see SWAT-looking police yelling at everyone to evacuate immediately," Alirani told Reuters.

UCLA, with more than 43,000 enrolled students, is in the Westwood section of Los Angeles and one of the more well-regarded schools in the University of California system, known for its successful sports program.

Police received multiple calls of shots fired around 10 a.m. (1700 GMT), triggering an immediate search for suspects and victims by LAPD and campus police, officials said.

Erica Roberts, a sophomore economics major from Rockville, Maryland, said she took shelter inside the student health center about 10 minutes after she had arrived for work there.

"Everyone is really on edge and contacting loved ones to let them know we are safe," she said in a telephone interview. "I'm trying to stay in contact with all my friends on campus to make sure they are OK. Everyone is just terrified."