The Department of Homeland Security’s Cybersecurity and Infrastructure Security Agency (CISA) is urging certain chemical facilities in the U.S. to strengthen their cyber and physical security defenses following recent military blows traded by the U.S. and Iran.

“In light of recent international events with the potential for retaliatory aggression against the U.S. and our critical infrastructure, CISA urges facilities with chemicals of interest—whether tiered or untiered under the Chemical Facility Anti-Terrorism Standards program—to consider enhanced security measures to decrease the likelihood of a successful attack,” CISA said in a new Insights bulletin issued on Tuesday.

Chemical facilities are tiered based on a dynamic risk assessment methodology used by CISA.

Following a U.S. strike that killed a key Iranian military commander and Iranian threats to strike back, DHS issued a terrorism advisory highlighting past Iranian cyber operations against various industries and government facilities. Iran eventually retaliated with missile strikes against two U.S. air bases in Iraq.

CISA is not requiring tiered chemical facilities to implement the enhanced security measures but recommended a range of actions be taken, including increasing awareness and organizational vigilance, exercising incident response and crisis management plans, taking various cyber actions such as back up critical information, refreshing staff training and conducting vulnerability scans, and taking physical precautions to include inventorying chemicals and assets, confirming important community contacts, and increasing facility monitoring.