Yemen's Houthi rebels have declared an "emergency state" in Sanaa and issued a ban on partisan activities ahead of the 35-year anniversary of former president Ali Abdullah Saleh’s political party.
The rebel movement issued a written statement on Tuesday night entitled "Facing escalation with escalation", warning supporters of the General People's Congress party to avoid congregating in public places.
Local residents now fear clashes could break out ahead of a rally organised by the GPC for Thursday, the day of the anniversary.
Minister of State for the UAE, Anwar Gargash, said that "the GPC will face a historic test tomorrow in the Al Sabeen Square in Sanaa, his [Saleh's] decision to undo the insurgency, will be a decision for the future of Yemen".
It comes as the Houthis look poised to break off relations with Mr Saleh. The Iran-backed rebels have formed a political and military alliance with the former president and renegade soldiers loyal to him against the government of Yemeni president Abdrabu Mansur Hadi.
Separately, Yemen's Houthi rebels on Wednesday warned Mr Saleh, until now their main ally in the country's war, that he would "bear the consequences" after calling the Iran-backed rebels "militias". The rebels' leader Mohammed Ali Al Houthi demanded Mr Saleh apologise for doing so.
"What Saleh said went beyond a red line that could have happened only because he [Saleh] was besieged by evil, deposed from every evil and patriotism, religion, customs and ancestors disguised as a river of holy blood," said the Houthi statement.
"The dignity of the blood of our comrades, the martyrs and the wounded, refuses to remain silent or to sleep peacefully."
Local sources said the presence of armed supporters from both sides has intensified across Sanaa since the Houthis' statement on Tuesday, which came after a meeting between the Houthi leadership and members of various political parties, local media reported.
The marriage of convenience between the Houthis and Mr Saleh appeared to have fractured earlier this week after speeches from both sides accused the other of jeopardising their partnership.
Rebel chief Abdul Malik Al Houthi and Mr Saleh exchanged mutual accusations of back-stabbing in televised speeches.
Tension has been rising for days in the Yemeni capital, which is jointly controlled by Mr Saleh and the Houthis.
Yemen's war, which pits the Saudi-backed government against the Saleh-Houthi alliance, has claimed thousands of lives since 2015 and pushed the country to the brink of famine.