Most critical is the situation in the city of Sa'ada, where the population - including 35,000 internally displaced persons (IDPs) - has been trapped due to the clashes, Andrej Mahecic, spokesperson for the UN High Commissioner for Refugees, told reporters.

The city has been cut off from the rest of the world for over two weeks, and roads to the city are extremely dangerous as the clashes continue, with many roadblocks and checkpoints have been set up. Further isolating the area is the state of emergency and 12-hour curfew in place.

Information from Sa'ada, the capital of the governorate of the same name next to Yemen's border with Saudi Arabia, is scarce since both mobile and Internet networks are down, Mr. Mahecic said.

In addition to air strikes and mortar attacks, street fighting has erupted close to the UNHCR field office, he noted, adding that one staff member with the agency has opted to stay with her family in the besieged city.

Sa'ada has had no water or electricity since 12 August. “Food reserves are running low and the situation is becoming untenable for families, many of whom are hosting friends, relatives or neighbours displaced by the street battles,” the spokesperson said.

High temperatures during the day and heavy rains at night have left civilians, many of whom are observing the fasting period of the Islamic holy month of Ramadan, in dire need of food and clean water.

The fighting between Government forces and the Shiite rebel group known as Al Houthi has spread to neighbouring southern Amran province and Al Jaw province, to which UNHCR has no access to the 4,000 IDPs needing shelter.

UNHCR estimates that 150,000 people have been affected by the Yemen conflict since 2004, including those forced from their home by the latest round of hostilities.

Earlier this week, the UN, the Yemeni Government and several humanitarian organizations launched an urgent appeal for $23.5 million to provide food and shelter to uprooted Yemenis.

“The civilian population in this part of northern Yemen has suffered from the combined effects of extreme poverty, protracted absence of health facilities, and insecurity for years before this latest crisis,” Under-Secretary-General for Humanitarian Affairs John Holmes said. “Following this latest wave of displacement, needs are now acute.”#