Clashes raged in Yemen killing at least 27 people on Thursday, military officials said, despite a truce announced by US Secretary of State John Kerry.
Fighting between forces loyal to President Abedrabbo Mansour Hadi and Shia Houthi rebels and their allies intensified on the outskirts of the flashpoint city of Taez, killing four soldiers and five insurgents, the officials said.
Pro-Hadi forces pressed on with a three-day-old offensive to recapture the presidential residence and police headquarters in the southwestern city, they said, as rebels brought in reinforcements.
Further to the east, seven rebels and five soldiers were killed in clashes in Shabwa province, as both parties fought for control of the oil-rich Usaylan region, other military sources said.
Meanwhile, warplanes from the pro-government Saudi-led Arab coalition pounded rebel positions in Saada, the northern fiefdom of the Houthis, as well as in Nahm and Sarwah, close to the rebel-held capital Sanaa, they said.
Six other rebels were killed in an ambush in the central province of Baida, the officials said.
The fighting has shown no sign of abating despite Kerry's announcement of a new ceasefire starting on Thursday.
The US chief diplomat said on Tuesday that rebels were ready to observe a ceasefire plan taking effect from November 17, but the Yemeni government said it was not aware of any new peace initiative.
Kerry spoke a day after meeting Houthi negotiators in Oman.
The Houthis and the party of their ally, former president Ali Abdullah Saleh, confirmed their commitment to the truce, in a statement on the rebel television channel Almasirah's website.
Six attempts to clinch a ceasefire in Yemen have foundered, including a three-day October truce that fell apart as soon as it went into force.
It was designed to allow aid deliveries to millions of homeless and hungry Yemenis.
The UN says more than 7,000 people have been killed and nearly 37,000 wounded in Yemen since the Arab coalition launched a military campaign in March 2015 in support of the government against the Iran-backed rebels.