Washington DC [US], September 20 : The United States on Saturday (local time) urged Americans to reconsider travel to and through the Middle East amid heightened regional tensions, warning of possible rapid escalation, flight disruptions and attacks targeting US interests, as Yemen's Houthi fighters launched missile and drone attacks towards Saudi Arabia.
In a worldwide caution issued by the US Department of State, Americans currently in the Middle East were advised to exercise heightened vigilance and remain prepared for possible flight cancellations, airspace closures and other travel disruptions. The department also warned that Iran and groups supportive of Tehran could target US interests, businesses and institutions overseas. 
“Due to tensions in the Middle East, the security environment remains complex with the potential for unforeseen escalation,” the State Department said in its advisory.
The warning came as Saudi Arabia reported that a ballistic missile launched by Yemen's Houthis towards Riyadh was intercepted. The Saudi-led coalition also said the Houthis attempted to target civilian infrastructure in Bisha, Taif, Farasan and Yanbu. 
For Saudi Arabia, the US Department of State has maintained a Level 3 - Reconsider Travel advisory. The department cites the risk of Iranian drone and missile attacks targeting American interests, armed conflict, terrorism, exit bans and local laws concerning social media activity. 
The State Department said Iranian missiles and drones have previously targeted cities, infrastructure, airports, military bases, diplomatic facilities and energy installations in Saudi Arabia. It also warned that falling debris from intercepted projectiles could pose a risk.
US government employees in Saudi Arabia face additional restrictions, including a prohibition on travel within 20 miles of the Yemen border. Special authorisation is required for travel to Jizan, Asir, Najran and Qatif. 
The department also warned that commercial flights from Saudi Arabia remain operational but have faced significant disruptions amid the conflict.
Meanwhile, Yemen remains under a Level 4 - Do Not Travel advisory, with the State Department citing terrorism, armed conflict, kidnapping, unrest and other security risks. 
The latest advisory comes amid renewed fighting involving the Houthis in Yemen and Saudi Arabia.
According to Al Jazeera, Saudi Arabia-led coalition forces said the Houthis fired a ballistic missile towards Riyadh early Saturday, which was intercepted and destroyed. Coalition spokesperson Major General Turki al-Maliki said the Houthis had also attempted to target civilians and civilian infrastructure in Bisha, Taif, Farasan and Yanbu.
Saudi Arabia issued emergency alerts across the kingdom overnight on Friday, warning of a “hostile aerial threat”. Al Jazeera reported that at least one explosion was heard in Riyadh on Saturday, while residents near the airport reported seeing a large plume of black smoke. Saudi authorities reported no casualties or damage.
Al Jazeera reported that it was the first air raid alert in Riyadh since fighting between Saudi-backed forces and the Houthis escalated in July.
Meanwhile, Houthi military spokesperson Yahya Saree said the group had targeted “sensitive” sites in Riyadh and an Aramco oil facility in Yanbu using cruise, ballistic missiles and drones.
Al Jazeera quoted Yasmeen al-Eryani, executive director for knowledge production at the Sana’a Center think tank, as saying the Houthis appeared to be determining the timing and level of escalation.
On the ground in Yemen, Al Jazeera reported renewed clashes in Marib, Taiz, Lahj, al-Jawf and al-Bayda. Saudi-backed government forces said they had thwarted a Houthi infiltration attempt in southern Marib, while reporting casualties among Houthi fighters and Yemeni soldiers.
Al-Eryani told Al Jazeera that military options against the Houthis remained limited because much of the fighting was taking place in difficult mountainous terrain. She said containing the group could currently be more realistic than seeking to defeat it militarily.
The US State Department has separately maintained a Level 3: Reconsider Travel advisory for Israel.
The department also warned that US diplomatic facilities and American interests could face threats from Iran and groups supportive of Tehran, including at locations outside the Middle East.