Striking oil workers closed refinery operations across Mexico Wednesday to protest the arrest of their union boss following a gunbattle in which a federal agent was slain.

Joaquin Hernandez Galicia's arrest on gunrunning charges Tuesday was widely seen as a challenge to the powerful union accused of corruption by the new administration of President Carlos Salinas de Gortari.Attorney General Enrique Alvarez del Castillo denied it was an attack on the union, saying: "It is the prosecution of crime committed by individuals."

Notimex state news agency said soldiers blew down the union boss's door with a bazooka rocket when they raided his home Tuesday in northeastern Ciudad Madero city. Alvarez told a news conference a federal agent was killed in the ensuing shootout with Hernandez's bodyguards.

Police confiscated 200 Uzi machine guns and 250,000 rounds of ammunition at the house, Alvarez said.

His spokesman, Carlos Torres, announced 34 people have been arrested, including union Secretary-General Salvador Barragon Camacho and his predecessor, Jose Sosa. Sosa and 16 others were held on illegal weapons charges.

The Petroleum Workers Union of the Mexican Republic controls more than half the lucrative drilling contracts issued by the government oil monopoly Pemex, or Petroleos Mexicanos, S.A.

Authorities charge the union resells contracts or collects hefty commissions from drilling companies which pass the charge on to Pemex.

"We had to move to clean up things," a presidential source said on condition of anonymity. "They knew this was coming."

Hernandez Galicia last week warned the union would paralyze Mexico's oil industry if the government carried out threats to sell Pemex operations to private investors.

Oil revenues are crucial to the struggling Mexican economy and Salinas, who took office Dec. 1, has vowed to sell or close unprofitable state industries.