A general view of the ruins of the house of a Yemeni army commander loyal to the Houthis after it was hit by two airstrikes allegedly carried out by the Saudi-led coalition in Sana’a, Yemen, July 6, 2015. (Yahya Arhab/EPA)

The ongoing humanitarian crisis in Yemen took a deadly turn for the worse this week, with nearly 200 killed on Monday alone as a senior international aid official said the country's situation is a "catastrophe."

According to Yemen's Houthi-controlled state news agency Saba, at least 63 civilians died when Saudi-led coalition jets bombed Amran Province, in Yemen's north. Thirty of the deaths, it said, occurred at a market. Reuters also reported the deaths of some 60 people in a separate attack on a market in the southern town of al-Foyoush.

Those bombings came just two days after the UN reported a rocket attack struck a kindergarten in Aden, killing 12 refugees who were sheltering there.

"Since the closure of schools across Yemen at the end of May, schools and kindergartens were used to accommodate internally displaced persons," Adrian Edwards, a spokesperson for the UN's refugee agency, UNHCR, said Tuesday.

"Refugees and internally displaced families were among the most vulnerable, and the UNHCR thus again called on all parties to allow unfettered access for humanitarian aid," added Edwards.

Mohamed Elmontassir Hussein, International Rescue Committee's Yemen country director, told VICE News the humanitarian situation in Yemen is a "catastrophe."

"You have conflict going on on all sides, then you have all these diseases, which are actually expanding and escalating as we speak," said Hussein. "Overall, you might not have safe accessibility to provide any humanitarian support, or any support."

Meanwhile, the UN's human rights office reported on Tuesday that 1,528 civilians had died since the start of Saudi-led strikes in late March. Those totals did not include the most recent casualty tolls.

On June 28, an airstrike hit and partially destroyed a UN Development Program office in Khormaksar, Aden, wounding one civilian. Offices of the International Organization for Migration have been hit twice, once by an airstrike, and once by a mortar.

Last week, as talk of a humanitarian pause between the Saudis and Houthi rebels failed to muster any agreement, the UN raised Yemen's humanitarian crisis status to Category 3, the highest level. The UN's Office for the Coordination of Humanitarian Affairs (OCHA) warned that 21 million Yemenis — roughly 80 percent of the country — are in need of some form of humanitarian aid. More than 1 million Yemenis have been displaced by the combined toll of ground fighting involving Houthi rebels backed by Yemen's former president Ali Abdullah Saleh, and the Saudi-led aerial campaign targeting the Houthis that began in late March. The Saudis' professed goal is to reinstate Yemen's current president Abd Rabbuh Mansur Hadi, who has fled to Riyadh.

Since launching strikes, a Saudi naval blockade has also cut the supply of goods and fuel to a trickle, worsening the food supply situation in what was already the Arab world's poorest country.

According to the UN, fuel imports — which play a key role in transporting food and medical supplies, running hospital generators, pumping and cleaning water, and milling imported grains — are at 11 percent of their pre-conflict levels. Since March, diesel prices have risen 480 percent. The UN's children's agency (UNICEF) says that more than 500,000 children under five-years-old are at risk of "developing severe and acute malnutrition" in the next year.

With sanitation and public health services all but nonexistent in wide swaths of the country, aid officials say even if a ceasefire is reached, the task of saving lives is overwhelming.

"Over 20 million people now can't access clean water in Yemen, up from 12 million before the air campaign began," Grant Pritchard, head of policy for Oxfam in Yemen, told VICE News. "What's clear now more than ever is the situation is spiraling out of control."

In the contested southern Yemeni city of Aden, local authorities last week reported more than 8,000 cases of dengue fever — twice as many as it did just two weeks prior.

"There are 150 new cases of dengue every day, and 11 deaths per day, in Aden," Jonathan Bartolozzi, Mercy Corps Yemen director, told VICE News. "Streets have not been cleaned in months, trash has accumulated and pools of stagnant water are all adding to the worrying hygiene and health conditions."

Bartolozzi said that malaria, which is traditionally more of a concern in Yemen's western costal areas, is also being recorded in Aden. "As July is traditionally the start of malaria season, this is becoming more of an issue now," he said.

Aid workers are also watching for cholera outbreaks, which could linger for many months and potentially kill thousands.

The UN has issued a call for $1.6 billion in humanitarian aid for Yemen. Of that, just $273 million — about 13 percent — has been donated. That total does not include a $274 million pledge the Saudi government made in April, which at the time completely met an emergency "flash appeal" issued by the UN's Office for the Coordination of Humanitarian Affairs (OCHA). The Saudis have yet to deliver any of the money, despite announcing late last month that some $244 million had been allocated among nine UN agencies.

The Saudis have further insisted that the money be delivered through the newly created King Salman Center for Relief and Humanitarian Works. In an arrangement that some aid officials have described as strange and problematic, the UN signed off on a deal that will see the Center reach individual memorandum of understandings (MoUs) with each aid agency. An internal memo outlining that arrangement was sent by OCHA chief Stephen O'Brien to humanitarian partners last month and later obtained by VICE News.

Last week, more than a dozen humanitarian non-profit organizations operating in Yemen sent a letter to the UN's regional humanitarian coordinator for Yemen, Amer Daoudi. In the message, which was also obtained by VICE News, the groups told Daoudi they were "increasingly concerned about the risks to principled humanitarian action in Yemen arising from politicization of funding by donors who are direct belligerents in the conflict, namely the Kingdom of Saudi Arabia."

The NGOs further requested that Daoudi negotiate MoUs that would maintain the impartiality of relief operations, while ensuring that they not be publicly associated with the "KSC, Saudi Arabia, the Yemeni government in exile or other direct parties to the conflict." The NGOs asked that Daoudi guarantee that identifying information for those receiving aid are not disseminated to the Saudis or other belligerent parties.

If or how the Saudi pledge is eventually delivered remains an open question. Several aid workers and officials involved in the Yemen response told VICE News they didn't see the point of MoUs unless the Saudi government was trying to implement precisely the restrictions they have warned would endanger normal humanitarian operations.

"We don't know if it's going to come or not, but its more than two months now and nothing has come through," said the International Rescue Committee's Hussein. "I don't know whether the MoU will solve anything."

Other aid workers said that even with cash in hand, aid agencies and NGOs still wouldn't be able to reach many parts of the country, and that ending the blockade was a more pressing concern.

Though the Saudis control the air and seas around Yemen, both sides of the conflict have interfered with access, creating complicated restrictions that aid workers and locals must navigate.

On Tuesday, Cécile Pouilly, a spokesperson for the UN's human rights office said they had "received reports of very serious constraints to humanitarian access in Aden, al-Dhali, Taiz and Lahj, where Houthi-affiliated Popular Committees and armed forces loyal to former President Ali Abdalla Saleh have set up checkpoints controlling entry and exit of goods."