At least two tribesmen were killed and six others injured on Thursday after Houthi militants opened fire on a pick-up carrying people from Yemen's Marib province.
Sources said the incident happened near a military camp in the Khawlan district outside Sanaa at a time when Houthi militias are trying to takeover the oil-rich Marib.
Houthis have been besieging the camp which is part of the 7th military brigade since last night, the sources said.
This week, Houthis carried out a coup against transition president Hadi months after they seized the capital.
Observers said the coup will pave the way for Houthi takeover of Marib, which Houthi militants have failed to seize after months of battles in adjacent Jawf and Baidha provinces.
Marib tribes have been mobilizing to prevent a possible Houthi takeover raising concerns about the country's largest oil, gas and electric power projects in the province. Any violence will lead to the shutdown of all projects and then deepen woes.