CARACAS, Venezuela (AP) _ Two masked men threw explosive devices at a candidate for Venezuela's constituent assembly on Wednesday, injuring four university students but leaving the candidate unharmed.

The attackers fled the scene and were not caught, police said.

Alberto Franceschi, an outspoken critic of President Hugo Chavez, was about to begin a speech at a university in Valencia, 90 miles southeast of Caracas, when the explosives went off on the speakers dais.

Pieces of the table hit four college students, causing minor injuries, witnesses said.

Franceschi blamed members of Chavez's leftist Patriotic Pole coalition for the attack.

``I haven't the slightest doubt that the people from the Patriotic Pole, who habitually provoke sympathizers to protest violently against the government's opponents, are responsible,'' he told reporters.

Such assaults are becoming more frequent in Venezuela. Chavez supporters attacked two leading opposition politicians last week, shoving them as they left Congress.

Franceschi is a candidate in July 25 elections for a constituent assembly which will rewrite Venezuela's constitution. The assembly is the centerpiece of Chavez's governing agenda.