MANILA, Philippines - Dozens of male students ran naked on Friday around the University of the Philippines campuses in Quezon City and Manila, calling for cleaner rivers and greater efforts to save the earth.

In what has become an annual tradition at UP, fraternity members dashed through the halls wearing only masks to hide their faces and carrying signs calling for environmental protection.

The group adopts a cause every year, and this year, they teamed up with environmental groups to clean 20 polluted rivers and streams in Manila.

The annual run is said to have begun in the 1970s, when the fraternity members ran naked around the campus to protest former President Ferdinand Marcos' censoring of a film criticizing his administration.

Hundreds of onlookers packed the halls to watch, although not everyone was clear about the message.

"Whatever their advocacy was, I think it will definitely be heard and exposed," said Mariel Abao, a tourism student.

"Even though they have a weird way of expressing it, at least the issue is given light." - with a report from Reuters