Water and food shortages are being reported in the Yemeni city of Aden amid ongoing deadly fighting.
The UN says at least 500 people have been killed in battles between forces loyal to the exiled president Abd-Rabbu Mansour Hadi and Houthi rebels.
Saudi Arabia is leading a coalition of countries attempting to reinstall Hadi as president and stop the advance of the rebels.
Coalition fighter jets have been carrying out airstrikes for 11 days now.
The Houthis are allied to Iran and are fighting alongside soldiers loyal to former president Ali Abdullah Saleh.
The coalition is now said to control Yemen’s ports and air space, but the airstrikes do not appear to have halted the advance of the Houthis.
Witnesses say fighting continued on Monday and some reports say a foreign warship has been shelling Houthi positions.
The last bastion of those supporting exiled- president Hadi is in Aden.
As well as the food shortages in the city, some of the main suburbs have been without power for days after a generator was hit by an airstrike.
After days of negotiations the International Committee for the Red Cross has been given approval by the Saudi-led coalition to deliver aid to Yemen.
However, the charity says there are problems chartering an aircraft and the delivery of 48 tons of aid, mostly medical supplies, could be delayed by at least a day.
Red Cross spokeswoman Marie Claire Feghali is quoted by the Reuters news agency as saying: “We are still working on getting the plane to Sanaa. It’s a bit difficult with the logistics because there are not that many companies or cargo planes willing to fly into a conflict zone.”