UN Secretary-General Antonio Guterres has called for a ceasefire in Yemen in light of an ongoing humanitarian crisis, his spokesman said.
Mr Guterres "calls on all parties to the conflict to cease all air and ground assaults" and is "deeply concerned about the sharp escalation of armed clashes" over the past several days, spokesman Stephane Dujarric said.
"Ambulances and medical teams cannot access the injured and people cannot go outside to buy food and other necessities.
"Aid workers are unable to travel and implement critical life-saving programmes at a time when millions of Yemenis rely on assistance to survive," he continued, reiterating calls for the Saudi-led alliance to end their blockade of the country.
Three years after Huthi rebels captured the Yemeni capital Sanaa with the help of forces loyal to ex-president Ali Abdullah Saleh their alliance appears to be collapsing.
The two sides have fought deadly street battles this past week in Sanaa, in clashes the security sources say killed around 60 people.
The war in Yemen has claimed more than 8,750 lives since an intervention by Riyadh and its allies in March 2015 in support of a rebel government in the south of the country.