US President Donald Trump said Yemen’s Houthis were “misbehaving very badly” as the group stepped up missile and drone attacks on Saudi Arabia, but did not outline any specific US response.

“Well, the Houthis are misbehaving very badly. No good,” Trump told reporters late on Monday as he departed the White House for Ohio, when asked what he planned to do about the group.

The remarks came after repeated Houthi attacks on Saudi Arabia, including strikes on King Khalid International Airport in Riyadh that killed at least 13 people and wounded more than 300 over the weekend.

Saudi authorities have extended the suspension of operations at Riyadh’s airport until Saturday.

Trump said on Saturday that he was considering US military action against the Houthis following the airport attack.