SANA, Yemen — About a hundred people have been killed by airstrikes across Yemen in the past three days as warring parties have haggled over the terms of a humanitarian cease-fire, health workers and security officials said.

The airstrikes were carried out by a military coalition led by Saudi Arabia that has been trying for months to defeat the Houthis, a Shiite rebel group from northern Yemen. The two worst episodes came Monday when bombs struck markets near the southern port city of Aden, killing 40 people, residents said, and in Amran Province in the north, killing 40 more, according to a local security official. Smaller groups of casualties were reported in separate attacks.

Doctors Without Borders, which operates several medical facilities in Yemen, said in a statement that hundreds of people had sought treatment in recent days after being wounded in airstrikes and random shelling across the country.