The first air strike on Tuesday hit a “crowded popular market” in Taez province, killing 54 civilians including eight children, and wounding 32 others, he said in a statement.
The second raid was in the Red Sea province of Hodeida and killed 14 people from the same family, the statement said.
“I remain deeply disturbed by mounting civilian casualties caused by escalated and indiscriminate attacks throughout Yemen,” McGoldrick said.
In addition to the casualties from Tuesday’s two air raids, another 41 civilians were killed and 43 wounded over the previous 10 days of fighting, he said.
The Arab coalition intensified its air campaign targeting the Iran-backed Huthi rebels after December 19 when Saudi air defences intercepted a ballistic missile the insurgents fired at the Saudi capital Riyadh.
“These incidents prove the complete disregard for human life that all parties, including the Saudi-led coalition, continue to show in this absurd war that has only resulted in the destruction of the country and the incommensurate suffering of its people,” McGoldrick said on Thursday.
He said civilians “are being punished as part of a futile military campaign by both sides”.
“I remind all parties to the conflict, including the Saudi-led coalition, of their obligations under International Humanitarian Law to spare civilians and civilian infrastructure and to always distinguish between civilian and military objects,” he said.
The UN official said the conflict in Yemen has no military solution and could be resolved only through negotiations.
The Arab coalition intervened in support of the internationally recognised government in March 2015 after the Shiite Huthis took over the capital Sanaa and much of Yemen.
But despite the coalition’s superior firepower, the rebels still control the capital and much of the north.
More than 8,750 people have been killed since the coalition intervened, according to the World Health Organization.