Houthi rebels attacked targets in Yemen's Marib and Hadramout provinces and in southern Saudi Arabia, killing at least 18 Yemeni soldiers and wounding 11 civilians, officials said. The Yemeni military said at least 17 soldiers and an officer were killed in the attacks. The Saudi-led coalition said Thursday's strikes wounded 11 civilians in southern Saudi Arabia, an unprecedented toll in more than four years of hostilities. The US Embassy in Yemen condemned the attacks as cowardly, saying they represent terrorism against the Yemeni people and offered condolences to the families of the slain soldiers. Saudi Arabia warned of further Houthi attacks. The violence has raised concerns that the Middle East crisis is intensifying, with Yemen increasingly drawn into the US-Israeli war with Iran and the Houthis stepping up attacks on both government forces and Saudi Arabia, a key US ally. The Yemeni military said the attack would only increase its resolve to restore state institutions and impose sovereignty over national territory.