From Geneva, the UN Office for the Coordination of Humanitarian Affairs said that estimates show over 121,000 people had been displaced inside Yemen since a Saudi-led coalition airstrike campaign targeting Shiite rebels began on March 26, with nearly half that number concentrated in the northwest.
"Humanitarian partners are providing assistance including water, sanitation and health services but the response is constrained by continued high insecurity due to airstrikes and fighting on the ground," spokesman Jens Laerke said.
A combined force of Shiite rebels and security forces loyal to the former president have taken over large swaths of the country, including the capital, Sanaa, and are bearing down on the southern port city of Aden, where troops loyal to the internationally recognised government are struggling to hold them off in street-to-street fighting.
Earlier in the day, Iran's foreign minister had called for a peace plan that includes humanitarian aid, dialogue and the formation of a broad-based Yemeni government, with no preconditions as to who would run Yemen imposed before dialogue between the country's different factions begins.
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On the ground in Yemen, fighting continued, with tribal forces loyal to the internationally recognised government advancing on a military base held by loyalists to former President Ali Abdullah Saleh outside the central city of Marib.
The fall of the Marib base would clear a path to the rebel-held capital.
In Omran province north of Sanaa, military officials said airstrikes hit one of the Houthi's main brigades from their northern strongholds.
Near the southern city of Aden, local fighters and airstrikes destroyed a convoy of pro-rebel fighters, witnesses and security officials said. All spoke anonymously either because they feared retribution or were not authorised to release the information.