The United Nations and Iran have voiced concerns over an increase in fighting in Yemen after air raids on the capital killed 14 people following the breakdown of UN-backed peace talks.
"The secretary general is deeply concerned about reports of increased fighting between various parties in Hajjah, Saada and Sanaa provinces including over the past few days," UN deputy spokesman Farhan Haq told reporters in New York.
"The reported escalation in fighting exacerbates the already dire humanitarian and human rights situation and the suffering of the Yemeni people."
Saudi-led coalition air strikes hit a factory in the capital on Tuesday, killing 14 people according to medics, and led to the closure of Sanaa's international airport.
The raids come less than 72 hours after more than three months of UN-brokered peace talks in Kuwait were suspended following the appointment by the rebels and their allies of a council to run Yemen.
The talks made no headway, but UN envoy Ismail Ould Cheikh Ahmed refused to call the negotiations a failure and said he would continue to consult with both sides to arrange further meetings.
Iran, which backs the Houthi rebels, called on Saudi Arabia to end coalition air raids.
Foreign ministry spokesman Bahram Ghasemi accused world powers on Wednesday of failing to act upon Riyadh's "continued destruction of the infrastructure of this country, killings of civilians and brazen, inhumane siege of an oppressed nation."
A Houthi spokesman said Tuesday that Saudi-led strikes also hit the rebel stronghold provinces of Saada, Hajja and Ibb, in north and central Yemen.
The UN says that more than 6,400 people, mostly civilians, have been killed in Yemen since the coalition air campaign began last March.