Suspected Basque (search) separatists detonated four small bombs in the troubled region Sunday, police said — a day after Spain's government made an unprecedented proposal for Parliament to endorse talks with the armed group if it renounced violence.

Two policemen and a security guard suffered minor injuries after inhaling toxic fumes at a chemical plant where one of the pre-dawn blasts occurred, police said.

The explosions came a day after Spain's ruling Socialist party said it is seeking other parties' support for a parliamentary motion supporting the start of talks with ETA (search) if the group renounces violence, although the negotiations would rule out concessions toward ETA's goal of Basque independence.

If ETA involvement is confirmed in Sunday's blasts, it would be an embarrassment for Prime Minister Jose Luis Rodriguez Zapatero (search).

The bombs exploded in four towns in Guipuzcoa province, the capital of which is San Sebastian.

The injuries occurred in Bergara, where the bomb targeted a chemical plant whose products include a powerful acid for industrial use, an official at the Spanish Interior Ministry office in San Sebastian said. An undetermined amount of acid leaked into a river, she said.

The four devices detonated in the span of about an hour starting at 3 a.m., police said. They targeted two chemical plants, a paint factory and a metalworks facility.

Ignacio Astarloa, the conservative Popular Party's top official for justice issues, urged Zapatero to withdraw his proposal for negotiations and not let ETA toy with him "as if he were a doll."

In a speech Sunday in the northwest Galicia region, Zapatero did not address the bombings. He said he would work for unity among Spanish parties to bring about the end of ETA, despite the Popular Party's angry opposition to his proposal for negotiations.

"It is what all Basque and Spanish citizens want," he said in Santiago de Compostela.

ETA has staged a string of mostly low-scale attacks over the past year but has not killed anyone since May 2003.

The government describes the group as seriously weakened by arrests, with 175 suspected members picked up over the last year alone.

ETA is blamed for more than 800 deaths since the late 1960s in its campaign of bombings and shootings since the late 1960s aimed at carving out an independent Basque homeland in lands straddling northern Spain and southwest France.