Regional tensions are rising after Houthis repeatedly attacked Saudi Arabia, and a senior Houthi official threatened a “swift and painful response” toward Washington if the United States launched military strikes against the group in Yemen.

Mohammed Al Bukhaiti, who is a member of the Houthi political bureau, stated that the group would react immediately to what he termed “aggression” against Yemen by the US. He cautioned that any counteraction may hit the U.S. and its interests anywhere in the region.

Saudi Arabia is reportedly turning to the U.S. for help in fighting attacks by the Houthis. Hostilities between a Saudi-led military coalition backing the internationally recognised government and the Iran-backed Houthis are part of the conflict in Yemen.

The current flare-up has brought into question regional security and energy infrastructure. The Houthis have reportedly attacked Saudi with their aim at oil facilities, tankers and transport hubs, such as the airport in Riyadh.

Over the Saudi capital, there were reports of explosions Monday night. The Saudi-led coalition stated that a Houthis’ missile had been intercepted and the group itself claimed it targeted the airport a second time. Later, the coalition said it had intercepted and destroyed two ballistic missiles launched towards the city of Khamis Mushait, in the south of Saudi Arabia, close to the border with Yemen. Saudi military bases have been attacked in nature previously in the area.

The developments came after a deadly attack this Saturday at the airport in Riyadh, in which 13 people are reportedly dead. Amidst the growing atrocities, US President Donald Trump has threatened to join Saudi bombings on the Houthis, saying he was thinking about going to the war in Bahrain. Sources also reported Riyadh’s previous request to the United States for help.

Trump, in his speech on Monday, lambasted the Houthis for what he called their “unacceptable behavior” without specifying any details of a possible military response from the United States.

American action might escalate the conflict and add to threats to energy supplies and road and rail lines in the area. The latest escalation of tensions highlights the uncertainties December has brought to the Yemen conflict and highlights the potential for further warfare to break out across the Middle East.