"There is no ceasefire at all," Major General Ahmed Assiri told AFP.
Huthi rebels and their allies had breached the truce since it took effect at midnight yesterday, including by firing mortars and rockets across the border into southern Saudi Arabia, he said, forcing coalition forces to respond.
"This is the same situation as the previous time when we called a ceasefire," Assiri said.
Since the coalition intervened in March 2015 to support Yemen's government, five previous ceasefires attempts failed.
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In one attack, a man and his daughter were wounded in the kingdom's Jazan region, according to Saudi civil defence authorities.
Assiri said coalition artillery and aircraft retaliated.
"We will respond to each violation. We will be reactive," he said.
The coalition says it remains committed to the truce.