Tens of thousands of residents fled the fighting along Yemen's Western coastline where fighters backed by Saudi-led coalition are engaged in fierce battles with Ansarullah forces.
Stephane Dujarric, the Spokesperson for UN Secretary-General Antonio Guterres, told reporters on Monday that about 5,200 families, or around 26,000 people, have sought safety within their own districts or in other parts of Hudaydah governorate, Middle East News reported.
"The number is expected to increase as hostilities continue," he said.
Earlier, UN human rights chief Zeid Ra'ad al-Hussein voiced concern that the Saudi Arabia and United Arab Emirates-led military operation in Yemen could endanger millions of civilians.
"I emphasise my grave worry regarding the Saudi and Emirati-led coalition's ongoing attacks in Hudaida - which could result in enormous civilian casualties and have a disastrous impact on life-saving humanitarian aid to millions of people which comes through the port," al-Hussein said on Monday.
The United Nations has announced that nearly 5,000 families have been displaced in Yemen's Western province of Hudaydah, whose capital port city has been under unprecedented attacks by a Saudi-led military coalition and militia loyal to the impoverished country's former government.
The UN Office for the Coordination of Humanitarian Affairs said in a statement released on Sunday that 4,458 households have been displaced from their homes in Hudaydah since early June, adding that at least 36 displaced families had already lost their entire livelihood as their farms were damaged in airstrikes by Saudi-led coalition earlier this month.
The Red Sea port of Hodeidah is of vital importance; it's the main distribution point for humanitarian and commercial supplies arriving in Yemen, which is going through a massive humanitarian crisis. Riyadh and its allies have repeatedly tried to blockade the docks, claiming that it was being used to smuggle arms to Ansarullah fighters.
Saudi-led forces have started the Hudaydah operation since Wednesday, while the UN has warned could cause up to 250,000 deaths.
Prior to the start of the coalition's siege, the UN stressed that an assault on the densely populated port city may cost up to 250,000 civilian lives, warning that the operation could leave millions of Yemenis without the "food and basic supplies needed to prevent famine and a recurrence of a cholera epidemic".
The United Nations has also expressed deep concern over the assault by the Saudi-led coalition in Hudaydah as rights groups warned about the catastrophic repercussions of the offensive, which is considered the largest battle of the three-year war.
"I am extremely concerned about military escalation in #Hodeida & their humanitarian & political impact," the UN special envoy to Yemen, Martin Griffiths, said in a tweet after Saudi-led forces launched an offensive on the key port.
UN Secretary-General Spokesperson Stephane Dujarric had also stressed that "we're extremely concerned about the situation around Hudaydah. Our colleagues in the area have started to take precautionary measures in terms of ramping up assistance and redefining contingency plans in case of this further escalation".
Lise Grande, the UN Humanitarian Coordinator for Yemen, had also said humanitarian agencies "fear, in a prolonged worst case, that as many as 250,000 people may lose everything - even their lives".
The UN warned that the likely "catastrophic humanitarian impact" would be worsened due to Hudaydah's key role as the point of entry for some 70 percent of Yemen's imports.
Saudi Arabia has been striking Yemen since March 2015 to restore power to Mansour Hadi, a close ally of Riyadh. The Saudi-led aggression has so far killed at least 16,000 Yemenis, including hundreds of women and children.
Despite Riyadh's claims that it is bombing the positions of the Ansarullah fighters, Saudi bombers are flattening residential areas and civilian infrastructures.
According to several reports, the Saudi-led air campaign against Yemen has driven the impoverished country towards humanitarian disaster, as Saudi Arabia's deadly campaign prevented the patients from travelling abroad for treatment and blocked the entry of medicine into the war-torn country.
Yemen is the world's largest humanitarian crisis with more than 22 million people in need and is seeing a spike in needs, fuelled by ongoing conflict, a collapsing economy and diminished social services and livelihoods.
The United Nations aid chief has recently expressed concern over the decline of food imports to Yemen amid restrictions put in place by the Saudi Arabia, warning that a further 10 million Yemenis could face starvation by year-end.
"I am particularly concerned about the recent decline of commercial food imports through the Red Sea ports," Mark Lowcock, the UN emergency relief coordinator, said in a statement.
Lowcock stated that commercial food and fuel imports remained "well short of pre-blockade averages", warning that "if conditions do not improve, a further 10 million people will fall into this category by the end of the year".