The return of Yemen's embattled President Ali Abdullah Saleh marks a turn in events, threatening to push the restive country into civil war as peaceful protests degenerate into chaos.
Saleh returned Friday from a stay of more than three months in Riyadh, declaring himself a saviour who was "carrying the dove of peace and an olive branch."
But fighting flared as dozens were killed in Sanaa after his arrival.
The violence which has been concentrated in the capital's north and centre has left 173 people dead since Sunday.
While elite Republican Guard troops fought with dissident army units in central Sanaa, security forces battled tribesmen loyal to opposition tribal chief Sheikh Sadiq al-Ahmar in Al-Hasaba, a district in the capital's north.
"He returned because he thinks that his military forces' situation on (the) ground has improved," said Yemeni analyst Abdulghani al-Iryani. "He came to impose a military solution."
Iryani expressed concerns of a "full-scale war" that might erupt between forces loyal to Saleh -- including Republican Guard troops commanded by his son Ahmed and other security forces led by members of his family -- and dissident troops.
Fares al-Saqqaf, head of the Centre for Future Studies in Sanaa shared Iryani's fears.
"With his return, I fear (an all-out) civil war might break out" in the deeply tribal country, said Saqqaf.
On Thursday, rival tribesmen joined the battles in Al-Hasaba where gunmen loyal to powerful dissident tribal chief Sheikh Sadiq traded fire with followers of Saghir bin Aziz, a tribesman loyal to Saleh who is also an MP and a Republican Guard officer.
Fighting between the two tribes however died down Friday as security forces battled the dissident tribal chief's men.
"Saleh's return has complicated the the political process that was about to take place," said Iryani.
Saleh's opponents had hoped that the veteran leader's June 4 departure to Saudi Arabia, where he was hospitalised for bomb wounds from an attack targeting his Sanaa palace, would keep him out of power.
On August 17 they created a 143-member National Council grouping the parliamentary parties of the Common Forum, which includes the influential Islamist party Al-Islah (reform), with young protesters.
A Gulf Cooperation Council initiative, by which Saleh transfers power in return for immunity from prosecution for himself and members of his family, was expected to see light over the past week.
GCC chief Abdullatif al-Zayani and UN envoy to Yemen Jamal Benomar arrived in Sanaa Monday to resolve the country's political dispute but the latest bloodletting has stalled the peace deal.
Zayani, who had been hoping earlier in the week to persuade all sides to sign on to the pact, left Yemen empty-handed on Wednesday.
Saleh has repeatedly refused to sign the plan. However, on September 12 he authorised Vice President Abdrabuh Mansur Hadi to negotiate a power transfer with the opposition.
"His surprise return does not promise well," said Fares al-Saqqaf, head of the Centre for Future Studies in Sanaa. "If he wanted to resolve the crisis he could have done that from abroad."
Saudi Arabia was expected to press Saleh to sign the Gulf-brokered plan or to keep him in Riyadh. But apparently the kingdom, a key political player in the region, allowed its embarrassing guest to leave.
"In the end, Riyadh's ability to drive change in Yemen has its limits, and it appears that the kingdom is choosing not to extend itself and impose a solution that is not viable on its own," said Christopher Boucek, an analyst with the Carnegie Endowment for International Peace.
"I would not view Saudi Arabia as fully backing the regime only, but rather trying to work out how best to achieve its interests in a very fluid and complex situation," he added.
Saleh "will not let go of power in any way. The protesters will also not agree to dialogue and will escalate their movement... In all cases, things are heading towards escalation," said Saqqaf.
"It is unclear how he (Saleh) intends to influence current events. The only way to address the present political crisis is through compromise, and none of the parties appear willing to compromise," said Boucek.
"In the meantime, conditions are rapidly deteriorating and more Yemenis are needlessly suffering and dying," he added.