The city has faced "unrelenting" shelling in 2 1/2 years of escalated fighting in the impoverished country.
The report commissioned by the U.N. Human Rights Council, which re-convenes next week, also takes stock of the disastrous human rights situation in Yemen over much of the last three years.
Al-Qaida, the Saudi-backed internationally recognized government, and Shiite rebels known as Houthis are fighting in a country with devastated public services — home to what the U.N. calls the world's biggest humanitarian crisis.
The report Tuesday points to continuing human rights violations, security vacuums, recruitment of child soldiers and punishing airstrikes by a Saudi-led, U.S.-backed coalition.
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