U.S. embassies across the Middle East early Sunday morning local time issued security alerts for American citizens in the region. 

“Due to tensions in the Middle East, the security environment remains complex with the potential for unforeseen escalation,” said the alerts issued by embassies in Israel, Saudi Arabia, Iraq, Kuwait, Lebanon, Jordan, Bahrain, the United Arab Emirates and Qatar.

The alerts did not state a specific threat, but called for Americans to “exercise heightened vigilance and be aware of potential flight cancellations, airspace closures, and travel disruptions.”

They cited the recent fighting between Saudi Arabia and the Iranian-backed Houthi militants in Yemen, noting that the conflict between the two sides “has the potential to escalate rapidly.”

Turki al-Malki, a spokesperson for the Saudi coalition fighting the Houthis, said in an earlier statement posted on X that Saudi forces had intercepted a ballistic missile fired at the capital city Riyadh on Saturday.

In recent weeks, fighting has intensified between Saudi Arabia and the Houthis, who have taken control of vast swaths of Yemen’s Red Sea coastline, along with several islands in the critical Bab el-Mandeb Strait, a move which has put more pressure on an already stressed global oil supply.

Saudi Arabia’s crucial East-West oil pipeline was damaged by drone strikes earlier this month believed to have been conducted by Iran-backed militias operating in Iraq, although no group has taken credit for the attacks. 

The Houthis have attempted a blockade on Saudi ports since July.