AMMAN, Jordan — A pledge by Saudi Arabia to halt its military operations in Yemen failed to stop ferocious fighting across the country on Monday as a humanitarian aid group warned that more than six million people were facing starvation because of the war.

Saudi Arabia, which leads an Arab military coalition that has been fighting Yemen’s Houthi rebels since March, said Saturday that it would pause its military operations for five days to allow for the delivery of humanitarian relief supplies. But there was no sign of a letup in the violence on Monday, dashing hopes that the Saudi declaration would lead even briefly to a broader truce.

The Houthis and their allies fought to advance in several provinces, shelling the southern port city of Aden and firing rockets across the Saudi border, according to local military officials and Houthi media outlets. The Saudi-led coalition carried out airstrikes in a fiercely contested province in southern Yemen where anti-Houthi fighters are trying capture an important air base, local military commanders told The Associated Press.