The U.N. humanitarian agency warned Tuesday that thousands of Yemeni civilians caught in fierce clashes between warring factions are trapped in an embattled northern governorate, an area that has become another flashpoint in the country's bitter war.

The number of displaced in impoverished Hajjah has doubled over the past six months, with over 5,300 families fleeing from the district and its surrounding area in the past weeks, according to the U.N. Office for the Coordination of Humanitarian Affairs (OCHA).

Hajjah's mountainous district of Kushar, only 50 kilometers from the border with Saudi Arabia has been isolated from the outside world, roads and all communication lines are cut and "thousands of civilians are reportedly trapped between conflicting parties," the U.N. and local residents said.

Over the past days, airstrikes by the Saudi-led coalition, which is fighting Iran-backed Houthi rebels on behalf of Yemen's internationally recognized government, killed 22 people, including women and 14 children in the area. "It is outrageous that innocent civilians continue to die needlessly in a conflict that should and can be solved," said Lise Grande, the U.N. humanitarian coordinator in Yemen.

Amid U.N.-led truce attempts, the five permanent members of the U.N. Security Council urged Yemen's warring parties to implement a peace deal in the port city of Hodeidah. The Houthi group and the Saudi-backed government agreed on a ceasefire and troop withdrawal in Hodeidah, an exchange of prisoners, and the reopening of humanitarian corridors to help millions of starving Yemenis, with international monitors to oversee things.

Saudi Crown Prince Mohammed bin Salman, the former Saudi defense minister, and Saudi Arabia's allies launched Operation Decisive Storm in March 2015. The ongoing war has resulted in the worst humanitarian crisis in the world, with an estimated 24 million people, close to 80 percent of the population, in need of assistance and protection in Yemen, according to the U.N. The World Health Organization (WHO) says some 10,000 people have been killed since the coalition intervened in 2015, but rights groups state the death toll could be five times as high.

Many atrocities have been reported so far, which reveals multiple violations of human rights. Saudi airstrikes have hit markets and hospitals, killing civilians. The U.S. is, by far, the largest supplier of weapons to Saudi Arabia. The United Arab Emirates (UAE) and its support for the coalition have been crucial to the war in Yemen.