Yemen's Houthi have achieved significant gains towards the strategic city of Marib, the internationally-recognised government's last northern stronghold, AFP reported.
Military officials in the pro-government forces said the Houthis have taken control of the northwest Kassara battlefront and made progress on western frontlines despite airstrikes by the Saudi-led coalition which backs the Yemeni government.
According to the sources, the battles have now moved to the Al-Mil area, nearly six kilometres from Marib city centre.
At least 65 fighters were killed in the battles over the past two days alone; including 26 pro-government troops, among them four officers, the sources said.
The Iran-backed Houthis rarely disclose their losses.
For a year and a half, the Houthis have been fighting pro-government forces to control the entire north of Yemen.
Marib and its surrounding oil fields make up the last significant pocket of government-held territory in the north, the rest of which is under Houthi control, including the capital Sanaa.
According to the UN Security Council, the fighting over Marib has put one million internally displaced persons at great risk, and threatens efforts to reach a political solution to the conflict in Yemen.