Venezuelan officials say at least four people were wounded after unidentified gunmen opened fire on university students returning from a protest against constitutional changes.

Authorities said late Wednesday that no one was killed in the violence. A government official had initially told local television that one person had died. The exact circumstances of the shooting remain unclear.

The violence erupted after thousands of university students marched to Venezuela's Supreme Court to demand it postpone a referendum on constitutional changes that would expand President Hugo Chavez's power.

The constitutional changes would eliminate presidential term limits, further President Chavez's socialist reforms and strip the central bank of its autonomy. They also would give authorities sweeping powers if a national emergency is declared, including detention without charges and controls on the news media.

Venezuela's opposition parties, human rights groups and the Roman Catholic Church have condemned the plan. Former Venezuelan Defense Minister Raul Baduel says the changes would amount to a coup d'etat by Mr. Chavez.

Some information for this report provided by AP, AFP and Reuters.