Yemen’s warring sides have deployed reinforcements to the outskirts of a strategic central district, a government military source said Monday, after Huthi rebels made significant gains in the nearby province of Al-Bayda. The possible fall to the rebels of the district of Bayhan, near the border with the government’s last northern stronghold of Marib, could pose a major threat to the government. The Iran-backed Huthis escalated their efforts to seize Marib in February, and the fighting has killed hundreds on both sides.