The United States government has issued a global security alert urging its citizens in Nigeria and around the world to exercise increased caution following American military strikes on Iran.

The State Department advisory, released Sunday, warned that shifting security conditions stemming from U.S. combat operations in Iran could disrupt travel and pose safety risks, including possible airspace closures that interrupt flights.

“Following the launch of U.S. combat operations in Iran, Americans worldwide and especially in the Middle East should follow the guidance in the latest security alerts issued by the nearest U.S. embassy or consulate,” the advisory stated.

The department advised Americans to enroll in the Smart Traveler Enrollment Program, known as STEP, to receive real-time security updates. It also directed citizens to monitor the U.S. Department of State Security Updates WhatsApp channel for additional guidance.

The alert follows coordinated strikes by U.S. and Israeli forces on Iranian targets that killed Supreme Leader Ayatollah Ali Khamenei, armed forces chief of staff Gen. Abdolrahim Mousavi and several senior commanders of Iran’s Islamic Revolutionary Guard Corps. Iranian authorities and regional observers estimate the strikes killed more than 200 people and wounded at least 700 others.

President Donald Trump said Sunday that Iran had initiated contact seeking negotiations after the bombardments and that he had agreed to the proposal. He offered no timeline for talks.