Three people have been shot to death on a university campus in the Philippines' capital region.

A man opened fire ahead of a graduation ceremony at Ateneo de Manila University in Quezon City on Sunday afternoon.

Investigative authorities say the dead include the former mayor of a southern city and a security officer.

They add that the gunman engaged in a shootout with a campus security officer and tried to escape by car before being detained by police.

President Ferdinand Marcos Jr. is due to deliver his first State of the Nation Address on Monday at the House of Representatives' building, which is about 7 kilometers from the campus.

The incident happened despite tough security arrangements that had been in place in the capital region, including a ban on carrying guns and setting up checkpoints.

Marcos has banned protest rallies near the lower house building during his speech although such demonstrations were traditionally allowed. He also stationed more than 22,000 police personnel around the venue.

Marcos expressed shock and sadness over the fatal shooting on his Twitter account.