ADEN - Three civilians were killed in east Yemen on Sunday when rockets fired by Iran-backed rebels hit a government hospital, the facility's director and a local official said.

The attack wounded 17 other people, said the director of the Marib General Hospital Authority, Shawqi al-Sharjabi. Pro-government forces, backed by a Saudi-led coalition battling the rebels for more than a year, have retaken most of the eastern Marib province from the Shiite Huthi insurgents and their allies.

However, the rebels still control northern and western parts of the oil-rich province east of the capital Sanaa, which has been held by the Huthis since September 2014. A government official in Marib city told AFP that rockets were fired by rebels from the Haylan mountains overlooking the provincial capital.

He said the attack, which killed a doctor, took place during a visit to the city by a government delegation. The rebel advance on Sanaa forced Yemen's internationally-recognised government last year to declare main southern city Aden a temporary capital. But President Abedrabbo Mansour Hadi and many government officials spend most of their time in Riyadh as they struggle to secure Aden and other parts of the country where Sunni jihadists have gained ground.

Sunday's attack comes as the warring parties prepare for a UN-brokered ceasefire on April 10 intended to pave the way for peace talks in Kuwait a week later. The planned truce was only agreed by the two sides after months of shuttle diplomacy by UN envoy Ismail Ould Cheikh Ahmed.

Previous UN-sponsored negotiations between the rebels and the government failed to make any headway, and a ceasefire announced for December 15 was repeatedly violated and abandoned by the Saudi-led Arab coalition on January 2. The United Nations says about 6,300 people have been killed in the war, more than half of them civilians. Moreover, Under a scorching sun, refugees who fled Yemen's war struggle on in a camp on Djibouti's rocky shores, a year after Saudi-backed air strikes began devastating their homeland. Over 2,000 Yemenis have made the Markazi camp their home, fleeing the Arabian Peninsula to Djibouti across the narrow Bab al-Mandeb straits -- the "Gate of Tears" in Arabic -- the key shipping channel of the Gulf of Aden.

"It's very hard. It's hot, there is nothing to do, nothing to eat, nothing to drink," said 36-year old Irsal Ismail, who has lived in the baking hot camp for a year. She fears the devastating effects of the 'khamsin', the ferociously hot sandy wind that will accompany the arrival of summer in the weeks ahead. "We will not be able to live in this place with the same thing we already experienced last year," she said softly.

Djibouti, a tiny nation of over 800,000 people, is a haven for Yemeni refugees fleeing the air strikes and battles against Huthi rebels that has left Yemen in ruins, but it offers little more than safety from the bombs.

Air strikes kill or maim six children a day in Yemen, the UN said this week. Over 173,000 people have fled the country since war began, according to the UN refugee agency (UNHCR), including 33,000 to Djibouti, across just 30 kilometres (20 miles) of sea from Yemen. Markazi camp on Djibouti's rugged northern Gulf of Tadjourah coastline is run by the UNHCR and the government's own disaster response agency, the National Office for Refugees and Disaster Victims (known by its French acronym, ONARS), which says it does what it can to help, but living conditions are tough.

"I was forced to leave Yemen because there was no more peace," said Hassan Din, 35, from Yemen's southern port of Aden. "But I came from war to find another war. Children have had hepatitis, malaria, they got sick because of the water. We can not find water or food."

Aden was badly damaged in months of fighting between pro-government forces and Shiite Huthi rebels, as well as Al-Qaeda's Yemen-based branch, one of the jihadist network's most dangerous franchises. Islamic State jihadists have also joined the battle in Yemen.