U.S. officials warned on Thursday that Russia may be targeting American defense companies in a potentially stepped-up sabotage campaign.

The new warning said that Russia’s intelligence services had conducted sabotage operations against European defense companies “in an attempt to undermine Allied support for Ukraine.”

Russia’s campaign, officials said, increases the risk to American companies overseas and, at least potentially, in the United States.

The warning was issued by the National Counterintelligence and Security Center, which advises American businesses on intelligence threats from potential adversaries.

The center often warns about attempts by the Russian and Chinese governments to steal intellectual property or potential cyberthreats against American businesses.

The alert issued on Thursday urged executives at defense companies to be on the lookout for surveillance near their facilities and staff, as well as for signs of trespassing or vandalism. Intelligence officials also said defense firms should be extra watchful for potential disruptions and should increase their physical and online security.