More than 14 hours after the deal was struck, an Associated Press reporter saw the Shiite rebel gunmen deployed outside the house of President Abed Rabbo Mansour, located west of the capital.
There was also no sign that the president’s chief of staff, who was kidnapped on Saturday, has been released – which was also part of the deal.
The militiamen are positioned outside the presidential palace, which they stormed after intense clashes.
The Houthis say they want better representation in government. A deal reached on Wednesday promised to respond to their demands.
Earlier, clashes erupted between Shiite rebels and tribesmen east of the capital, killing at least six people, according to Yemen tribal leaders.
The fighting 30 miles (45km) southeast of Sanaa threatened the tenuous deal reached late on Wednesday between the president and the rebels to end the violent stand-off in the capital.
The tribal leaders say two tribesmen and four gunmen allied with Houthi rebels were killed in the clashes in Khawlan-Watadah, a region leading to the central oil-rich province of Marib.
At the entrance of Marib itself, clashes also erupted between Houthis and local tribesmen over new checkpoints erected by tribal fighters.
The Houthis claim the government is not doing enough to fight al-Qaida militants in Marib.