University students walk out on US VP

Dozens of students walked out of Notre Dame University's commencement exercise on Sunday to protest a speech by US Vice President Mike Pence, who warned graduates of the prestigious Catholic school against suppressing free speech.

The protesters, among the thousands of graduates and guests assembled in the university's football stadium, stood up when the conservative Republican began his speech and streamed out of the ceremony, to the jeers of some of those who remained.

A few of the students had messages of protest attached to their traditional "mortarboard" graduation caps. One of them displayed an inverted US flag, a sign of protest popularized during the Vietnam War era, and the words "Are we great again yet?," a reference to President Donald Trump's campaign slogan.

In his speech at the Indiana school, Pence squarely addressed the festering controversy of what constitutes free speech on campus, an issue that has intensified at many universities since Trump's election victory last year.

"I would submit that the increasing intolerance and suppression of the time-honored tradition of free expression on our campuses jeopardizes the liberties of every American. This should not, and must not be met with silence," Pence said, in an apparent reference to efforts to bar him from speaking.