The leader of Yemen’s Houthi rebels has vowed to resist a Saudi-led bombing campaign that has been targeting his forces since late March.
In a televised speech, Abdul Malik al-Houthi said Yemenis would never give in to the Saudis’ “savage aggression”.
Hundreds have died as the rebels and allies battle government supporters, who are backed by the air campaign.
A BBC correspondent in the contested port city of Aden says its hospitals lack the supplies to treat patients.
Orla Guerin says medical teams in the city are complaining that they are overwhelmed and patients are dying for lack of equipment. They have appealed for more antibiotics and bandages.
The rebels and their allies have been trying to capture Aden for weeks, but have been held back by the air strikes and by forces loyal to Yemeni President Abedrabbo Mansour Hadi.
On Monday, a massive explosion was heard in the rebel-held Yemeni capital, Sanaa, reportedly from an air strike targeting a weapons store.
Over the weekend, more than 80 people are said to have died in air strikes and in clashes on the ground between the rival forces.
The international aid agency, Oxfam, has meanwhile condemned an air strike that hit one of its stores containing humanitarian supplies in Saada, a Houthi stronghold in the north of the country.
“The contents of the warehouse had no military value. It only contained humanitarian supplies,” an Oxfam official said, adding that the organisation had already provided the co-ordinates of its warehouses to the Saudis.
Meanwhile, in a televised address, Mr Houthi accused the Saudis of “malice and arrogance towards the Yemeni people”.
He warned that the bombing campaign aimed to strengthen al-Qaeda in Yemen. While criticising Saudi policy, Mr Houthi praised Iran as “a great Islamic country”.
Sunni-ruled Saudi Arabia has accused its regional rival, Shia Iran, of aiding the Houthis, who are from the Zaidi Shia sect. Iran is allied to the rebels but denies arming them.
The UN says 150,000 people have been displaced by the latest fighting, and some 12 million are short of food.
It has also said 731 people had been killed and 2,754 injured – many of them civilians – in three weeks between March and April. The numbers were likely to be an underestimate, it has warned.