An attempt last month at U.N.-led talks among Yemeni parties in Geneva failed to reach an agreement.

Last week the U.N. envoy for Yemen, Ismail Ould Cheikh Ahmed, said the country is "one step" from famine. He urged all parties to the conflict to agree to a humanitarian pause during the Muslim holy month of Ramadan, which ends July 17, to allow desperately needed aid to be delivered.

The U.N. now faces four top-level humanitarian emergencies, with Level 3 emergencies also Iraq, Syria and South Sudan. The U.N. humanitarian office said the declaration of a top-level emergency mobilizes U.N.-wide staffing and funding to scale up aid delivery.

Humanitarian chief Stephen O'Brien convened a meeting of U.N. agencies early Wednesday, and all agreed to declare a Level 3 humanitarian emergency in Yemen for six months.

The United Nations on Wednesday declared its highest-level humanitarian emergency in conflict-torn Yemen, where over 80 percent of the population needs assistance. U.N. officials have said the Middle East's most impoverished country is a step away from famine.

21 million Yemeni people are in desperate need of aid, including children who are caught in the middle of a conflict

The fighting in Yemen pits Houthi rebels — a marginalized group from the north — and allied troops loyal to former President Ali Abdullah Saleh against Sunni fighters, southern separatists, local and tribal armed groups and loyalists of President Abd Rabbu Mansour Hadi. The rebels seized the capital in September and swept south, forcing Hadi to flee to Saudi Arabia.

A Saudi-led and U.S.-backed coalition began launching airstrikes against the rebels on March 26, and a near-blockade of Yemen's ports has made it very difficult to deliver humanitarian aid.

International rights groups have condemned the blockade. “The rising civilian casualties from the fighting could become dwarfed by the harm caused to civilians by the coalition blockade on fuel, if it continues,” Human Rights Watch (HRW) director Joe Stork said in May. “It is unclear how much longer Yemen’s remaining hospitals have before the lights go out.”

The coalition's blockade of fuel is in violation of the laws of war, according to HRW. "Fuel should be allowed to go through whether or not a proposed cease-fire takes effect," said a statement on the group’s website.

HRW also blasted the coalition for 13 airstrikes in May that killed dozens of civilians and could constitute war crimes. It called on the U.S., which has provided logistical and intelligence support to the Saudi-led campaign, to press for an investigation into the airstrikes.

According to the World Health Organization's latest figures, 3,083 people have died as a result of the conflict, and 14,324 people have been injured, said U.N. deputy spokesman Farhan Haq.

He said over 21.1 million people in Yemen need aid, nearly 13 million face "a food security crisis," and 9.4 million have little or no access to water, raising the risk of water-borne diseases, including cholera.

He said 11.7 million people have been targeted for assistance under a revised U.N. humanitarian response plan.

Al Jazeera and The Associated Press