WASHINGTON — The United States joined Saudi Arabia in launching airstrikes against Houthi military targets in Yemen on Monday, the Pentagon confirmed, days after a Houthi missile struck Riyadh's main airport and left several people dead. The operation marked a sharp escalation in US involvement in the conflict.

President Donald Trump signaled over the weekend that Washington would decide quickly whether to join Saudi retaliation after the attack on King Khalid International Airport. Pentagon officials said the strikes targeted missile launch sites, weapons depots and command facilities in Houthi-controlled areas near Sanaa and Saada.

The Iran-aligned Houthi movement claimed responsibility for the Riyadh airport strike, describing it as retaliation for Saudi-led operations in Yemen. The group's spokesman, Yahya Saree, vowed further attacks on Saudi and American interests in response to any escalation, according to statements carried on Houthi-run Al-Masirah television.

The joint action drew immediate concern from humanitarian agencies. A United Nations Office for the Coordination of Humanitarian Affairs spokesperson warned that renewed bombardment risked worsening Yemen's already dire humanitarian situation and endangering civilian infrastructure. Saudi state media said the coalition had taken measures to limit civilian casualties.

The strikes deepened US entanglement in a regional conflict that has repeatedly disrupted shipping through the Red Sea and strained relations with Tehran. Analysts at the International Crisis Group cautioned that direct American participation could invite wider Houthi reprisals against Gulf states and maritime traffic.