CARACAS, Venezuela -- Venezuela's armed forces have stepped up protection of the country's strategic oil industry, a key supplier to the U.S. market, following the Sept. 11 attacks in the United States, officials said.

"Security has been reinforced at all installations across the country," an official from the state-oil company Petroleos de Venezuela (PDVSA) told Reuters. Venezuela was the second-largest supplier of crude oil to the United States in July.

"There is an alert out for possible threats of attacks," said the PDVSA official, who asked not to be named. He made clear the alert was not a response to a specific threat but was a general precautionary measure taken in light of last week's suicide attacks against the World Trade Center in New York and the Pentagon in Washington.

Venezuela's President Hugo Chavez has strongly condemned the Sept. 11 attacks, which left nearly 6,000 people missing or dead. In his message of solidarity, Chavez pledged to maintain stable oil supplies to the United States.

The PDVSA official did not give details of how security was being reinforced at the nation's oil installations, but Venezuelan newspapers reported the National Guard was deploying an elite commando unit to provide additional protection.

National Guard Commander Gen. Francisco Belisario Landis told the Caracas daily El Universal that an additional 500 special forces soldiers would join around 1,000 guardsmen already protecting refineries around the country.

After last week's attacks, PDVSA's U.S. subsidiary, Citgo, said it had increased security at all installations. Venezuela is a member of the Organization of Petroleum Exporting Countries, and Energy Minister Alvaro Silva has said the country is ready to increase oil exports should this be necessary and if OPEC members agree on such a move.