The truce has been repeatedly violated and the Saudi-led coalition warned it was close to abandoning the agreement, aimed at helping parallel UN-sponsored peace talks which opened Tuesday in Switzerland.
Delegates at the peace talks being held behind closed doors did not meet today as the rebels snubbed a morning meeting.
"Last night, they already expressed reservations," said a member of the government delegation, requesting anonymity.
Forces loyal to President Abedrabbo Mansour Hadi and allied tribesmen today captured Hazm, the capital of northern Jawf province, after making significant gains in the neighbouring region of Marib, tribal sources said.
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About 1,000 soldiers are involved in the operation in Haradh, an official said, adding that "intensive fighting took place" in the town, which has a population of around 25,000 people.
He said dozens of renegade troops loyal to ousted president Ali Abdullah Saleh and allied with the Iran-backed Shiite Huthi rebels had been killed.
The advancing force has reached just a few kilometres (miles) away from the Red Sea port of Midi, which has been under rebel control since 2010, military sources said.
It was the loyalists' first territorial advance in Sanaa province.
The coalition, meanwhile, said Saudi air defences had intercepted a ballistic missile fired from Yemen and that a second missile struck a desert area east of the Saudi city of Najran.
It warned that the ceasefire would not hold if such violations persisted.
Although the alliance wants the Switzerland peace talks to succeed, "it will not adhere to the truce for long given the threat to the kingdom's territory", it said.
But contrary to the coalition claim of shooting down a missile over Marib, Brigadier General Sharaf Luqman said a Tochka missile hit a base for "mercenaries" in Marib.