The report by the Office for the Coordination of Humanitarian Affairs came as warplanes from the Saudi-led coalition throughout the day Tuesday pounded positions of the Shiite rebels, known as Houthis, and allied troops loyal to ousted leader Ali Abdullah Saleh in the capital, Sanaa, and in the south.
The three cities of Dhale, Aden and Taiz "the third largest city in Yemen " have been declared "disaster zones" by the internationally-recognized government in exile, which said the humanitarian situation is on verge of collapse.
The Saudi- and Western-backed president, Abed Rabbo Mansour Hadi, was forced to flee abroad by the Houthi advance and is currently in the Saudi capital, Riyadh.
But so far, the air campaign has been unable to halt the Iranian-allied rebels.
More From This Section
In the early morning hours, multiple explosions shook Sanaa as warplanes struck several rebel-held army camps, trucks carrying weapons and houses turned into weapons' depots for the Houthis, according to residents and officials.
The US and Saudi Arabia and their allies accuse Iran of arming the Houthis, a claim that Tehran and the rebels deny, though the Iranian government says it gives the rebels humanitarian and political backing.
Heavy smoke blanketed Sanaa, said the residents, speaking on condition of anonymity because they feared for their own safety.
Other airstrikes hit in the southern port city of Aden, scene of weeks of fierce fighting as Houthis and pro-Saleh troops try to wrest the city from local militias and Hadi loyalists. Strikes Tuesday hit a police commando camp run by pro-Saleh commanders.