Government forces have clashed with Houthi rebels in the capital and launched air strikes targeting the movement's fighters east of Sanaa, a deal to end a weeks-long standoff into jeopardy.
Clashes broke out near a state TV building in the north of Sanaa, when troops stopped a rebel truck loaded with weapons, military officials told the Associated Press news agency.
Fighting also intensified in the restive Marib province, where the military launched air strikes targeting Houthi positions.
The authorities said a senior Houthi commander was killed in one of the raids.
The flare-up came despite the Houthis saying they were close to signing a deal reached with the government.
Al Jazeera's Hashem Ahelbarra, reporting from Sanaa, said an agreement had been reached about appointing a technocrat prime minister, and cutting fuel prices by almost 30 percent.
However, a stumbling block has been the Houthis demand that the deal be signed in their stronghold in the northern city of Saada, while President Abd-Rabbu Mansour Hadi wants to sign it in the capital.
The rebels, also known as Zaidis or Ansarullah, have been camped in Sanaa in a bid to oust the government, which they accuse of corruption.
Yemen has been locked in a protracted transition since longtime President Ali Abdullah Saleh was forced from power in February 2012 after a deadly 11-month uprising.
Source: Al Jazeera and agencies