The July 20 attack on the western port city of Hodeida, controlled by Yemen's Iran-backed Huthis, came a day after the rebels claimed responsibility for a drone attack on Israel's commercial hub of Tel Aviv.
New York-based Human Rights Watch (HRW) said the Tel Aviv strike that killed one person could also constitute a war crime by the Huthis.
The Israeli response decimated the Hodeida port's fuel storage capacity and killed at least nine people, according to the Huthis who hold much of Yemen including the capital Sanaa.
HRW said "at least six civilians" were killed in the strikes which "reportedly injured at least 80 others".
The rights group noted that the Hodeida port "is critical for delivering food and other necessities to the Yemeni population".
The damage "could have a long-term impact on millions of Yemenis who rely on the port for food and humanitarian aid", it said.
The Israeli military has said the Huthis used the Hodeida port to receive Iranian weapons.
The strikes "damaged or destroyed at least 29 of the 41 oil storage tanks at Hodeida port, as well as the only two cranes used for loading and unloading supplies from ships," HRW said.
It added that the attack also forced the Hodeida power plant offline for 12 hours.
"The attacks appeared to cause disproportionate harm to civilians and civilian objects. Serious violations of the laws of war committed wilfully, that is deliberately or recklessly, are war crimes," HRW said.
In November the Huthis began attacking ships in the Red Sea, a campaign they have said is meant to show solidarity with Palestinians in Gaza after Hamas's October 7 attack on southern Israel kicked off the ongoing war in the besieged territory.
The Huthis have also launched strikes on other Israeli port towns since the war began.
Yemen has been engulfed in a devastating conflict since 2014 between the Huthis and the internationally recognised government, supported by a Saudi-led military coalition.
The fighting has killed hundreds of thousands of people either directly or indirectly and triggered one of the world's worst humanitarian crises.
The Israeli strikes on Hodeida risk worsening conditions for millions of Yemenis in rebel-held areas, HRW said.
"Yemenis are already enduring widespread hunger after a decade-long conflict. These attacks will only exacerbate their suffering," said Niku Jafarnia, HRW's Yemen and Bahrain researcher.
