The father of one of Elliot Rodger's victims has urged students to fight for tougher gun laws during a memorial service in California.

Thousands of people gathered at the University of California, Santa Barbara to pay their respects to the six college students knifed and shot to death by the 22-year-old on Friday.

Christopher Ross Michaels-Martinez was one of the victims.

"It's time to stop the gun violence," said his father, Richard Martinez. "Our children deserve a land free from fear.

"It's almost become a normal thing for us to accept this. It's not normal.

"Any of us who grew up in the 50s, 60s, 40s know that life doesn't have to be like this. So why should it be like this for you people who are young now?"

Mr Martinez called on those inside a packed Harder Stadium to send a message to Washington by chanting "Not one more".

Students made 10,000 ribbons for the service as the university cancelled classes and declared a day of mourning.

"We are here because in this moment of loss there's a human desire to come together to reach out to one another for love and support," said University of California president, Janet Napolitano, a Democratic politician.

"We are grieving together today as a family, as the community of the University of California and we will get through this," said Ms Napolitano, the former secretary of homeland security.

Rodger, the son of an assistant director on The Hunger Games, stabbed his roommates Cheng Yuan Hong, George Chen and Weihan Wang to death. He later shot Veronika Weiss and Katie Cooper near their campus and Christopher Martinez at a deli.

Another 13 people were wounded in the attack in the town of Isla Vista.

The killer obtained three semi-automatic handguns and still had 400 unspent rounds of ammunition when he turned the gun on himself.

Rodger, who had previously convinced police he was not a threat to others, left several written manifestos and online videos explaining his motives.