Violence Escalates in Yemen as Ceasefire Set to Begin

Just hours before a proposed-ceasefire was supposed to go into effect, the fighting in Yemen intensified.

Saudi Arabia was slated to pause its bombing campaign on Monday at 4pm ET to allow much needed humanitarian aid to enter the country, according to a pledge made on Friday by Saudi Foreign Minister Adel al-Jubeir.

But in the meantime, the death toll has mounted. Saudi bombs killed 90 people, and wounded 300 in Yemen's capital Sanna on Monday, according to Yemeni health officials. Meanwhile, Houthi and anti-Houthi rebels battled block by block for turf in the strategic port city of Aden, and Saudi Arabia has declared the rebel stronghold of Sadaa a "war zone," warning all civilians to evacuate. Houthi and Saudi forces continue to exchange barrages of artillery fire across their 1,100 mile shared border.

"There's been a huge escalation in hostilities, making the need for a cease-fire immensely clear," Sheila Carapico, a leading Yemen expert and professor of political science at the University of Richmond, told VICE News. "The devastation is immense."

Video from Monday showed a massive explosion and fireball erupting over Sanaa after a Saudi airstrike appears to have targeted an ammunition store.

After the initial explosion, ammunition appeared to continue to burn and cook off at the site:

A Houthi spokesperson told the Guardian on Sunday that the Houthis would "cooperate with the ceasefire to help people suffering from the severe fuel and food shortages." But elsewhere, the Houthis have vowed to "respond" to violations of the truce — a sign that the five-day pause may not last long.

"What may happen is the Saudis will stop for an hour or two, and accuse of the Houthis of the violation, and resume bombing," predicted Carapico.

UN Special Envoy Ismail Ould Cheikh Ahmed arrived in Yemen just hours before the cease-fire was set to go into effect to plead with both sides to lay down their arms.

"We are convinced there is no solution to Yemen's problem except through a dialogue, which must be Yemeni," he told local reporters. "The call for a truce was echoed by Iran, an important ally of the Houthi Movement.

Fighting in Yemen has killed over 1,400 people in the last month, more than half of them civilians, according to the UN. In late March, the Houthis — a Shi'ite movement from the North that has long sought greater independence — routed the Yemeni army and took control of the capital Sanaa. President Abd Mansur Hadi found refuge across the border in Saudi Arabia, while his allies struggled to hold on to parts of the strategically important Yemeni city of Aden.

Related: A Yemeni Man Is Suing British Telecom over America's Deadly Drone Strikes

In recent weeks, the Houthi cemented an alliance with Yemen's former president Ali Abdullah Saleh, who had been ousted by popular protest during the 2011 Arab Spring. To force the Houthis out of the capital and reinstall their ally President Hadi, the Saudis have assembled a wide coalition, including Egypt, The United Arab Emirates, and most recently Malaysia.

Over the course of the conflict, both sides have been roundly criticized for flagrant violations of international law. Human Rights Watch has accused Saudi Arabia of using cluster munitions, "flouting the global standard that rejects cluster munitions because of their long-term threat to civilians." Meanwhile, HRW accuses the Houthis of recruiting child fighters.

With just hours to go before the cease-fire goes into effect, human rights activists are hoping the peace materializes so much-needed humanitarian aid can be flown into Yemen.

"The UN Refugee agency is making final preparations for a huge airlift of humanitarian aid" said Adrian Edwards, a spokesman for U.N. refugee agency. But that aid can only be delivered, he added, "If today's proposed ceasefire comes into effect and holds."

Follow Avi Asher-Schapiro on Twitter: @aaschapiro