Hundreds of university students in Phnom Penh demonstrated on Tuesday (April 25) against a proposed new Constitution to give President Lon Nol supreme power -- as Khmer troop reinforcements tried to fend off a Communist offensive which has cut the main supply route to the capital from Saigon.

Voting for the Constitution is due to take place on Sunday (April 30). As rioting continued today (Thursday), one student was killed and 19 injured when police fired on a stone-throwing crowd.

Students, said to be responsible for the resignations of several leading Khmer politicians, have been demonstrating since Marshal Lon Nol assumed the title of President earlier this month. Under a new ruling, all people under the legal voting age of 18 years are barred from political activities.

As the students demonstrated, the Khmer army was moving thousands of reinforcements into the tri-border area of Laos, South Vietnam and Khmer -- and Highway One, the main supply routs between Phnom Penh and Saigon.

Highway One has seen some of the bloodiest fighting in the Indochina conflict and despite helicopter airlifts of supplies, men and equipment, Khmer forces are still pulling out of firebases at the eastern end of the highway -- partly occupied by Communist forces.