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 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.
Jan 16, 2017 0
Special coverage on China's Two Party Sessions by The Daily Mail - People's Daily