Yemeni armed tribesmen arrived in Sanaa on Saturday in a bid to free top officials sieged by the powerful Shiite Huthi militia, tribal and defence sources said.
Representatives of tribes from Marib and Jawf provinces, joined by tribes from Sanaa, arrived in dozens of vehicles carrying armed men near the house of Defence Minister Mahmud Subaihi, a tribal source said.
The tribesmen have threatened to use force if necessary, a source told AFP, adding that both they and the Huthis have brought reinforcements to the neighbourhood around Subaihi's house.
Other tribesmen have also gone to the house of the head of intelligence, General Ali al-Ahmedi.
Both residences have been encircled since Thursday by gunmen from the Huthi militia, officially known as Ansarullah, as they tightened their grip on Sanaa.
The Huthis, who hail from the northern Saada province, overran Sanaa unopposed in September, and have since expanded to other regions south of the capital and coastal areas.
President Abdrabuh Mansur Hadi resigned Thursday after saying he could not stay in office due to a "total deadlock" in the country.
The situation in the capital has deteriorated since Huthis abducted a top aide of Hadi a week ago and went on to seize the presidential palace.