Forces loyal to Yemens government fought their way into the province surrounding the capital on Monday, tribal sources said, the closest they have advanced toward Sanaa since the Houthi movement seized it in September last year.
The advance comes despite a conditional agreement to extend a seven-day truce in Yemen, following a week of U.N.-sponsored peace talks in Switzerland in which the parties reached a broad framework for ending the nine-month-old war that has killed nearly 6,000 people.
"(President Abd-Rabbu Mansour) Hadis forces took control of two mountains in the Nihm district in Sanaa province," one tribal source said. The area is about 60 km (37 miles) north-east of the capital.
A military alliance of mostly Gulf Arab countries led by Saudi Arabia began bombing Yemens Houthi movement, an ally of Iran, in March to try to restore Hadis government and roll back gains made by the Iran-allied Houthis.
Yemeni forces loyal to Hadi, backed by alliance air strikes, have made a number of gains against the Houthis in recent weeks. But the Houthis, a tribal militia that hails from the Zaydi branch of Shiite Islam, remain in control of much of the northern part of the country.
On Friday, Hadi loyalists captured the city of al-Hazm, the provincial capital of northwestern al-Jawf province.
Both sides have accused each other of violating the ceasefire that began with the start of the peace talks on December 15.
U.N. Special Envoy Ismail Ould Cheikh Ahmed had voiced deep concern at "numerous reports of violations of the cessation of hostilities" and set up a mechanism to strengthen compliance, a U.N. statement said.
The peace talks are scheduled to resume on January 14. The location had yet to be set, although both Switzerland and Ethiopia are possible venues.
The parties also agreed to set up a military de-escalation committee and to develop a package of confidence building measures such as prisoner releases.