Security forces and backers of Yemen's embattled President Ali Abdullah Saleh shot dead nine protesters on Saturday, as Saleh said he would soon visit the US ahead of transferring power in February.
Dozens more demonstrators were hurt when tear gas and water cannons were used against thousands of marchers demanding that Saleh face trial, witnesses and medics said.
"Six of the dead were taken to the field hospital" at Change Square in Sanaa, the epicentre of anti-regime protests in the capital, the facility's director, Mohammed al-Abbahi, told AFP.
The bodies of three others were taken to a private clinic in the city, said Mohammed al-Sormy, a doctor there.
Saleh has faced waves of protests since January demanding an end to his 33-year-regime, and the resulting crackdown by his security forces has left hundreds of people dead.
The veteran strongman has agreed to stand down following a February 21 presidential election, but some of his opponents are furious that Saleh has secured an immunity deal as a condition for his departure.
The objective of the "March for Life" that turned deadly on Saturday was to press for Saleh and his top allies to face criminal charges for their roles in the violence committed against anti-regime protesters.
All of those killed Saturday had been shot, Abbahi said.
Tens of thousands of protesters who set off from the southern city of Taez on Tuesday for the 270-kilometre (167-mile) march to the capital had arrived in Sanaa in mid-afternoon but were blocked in a southern suburb.
Government forces blocked the streets leading to Sabine Square, adjacent to the presidential palace, where Saleh loyalists have previously gathered on Fridays to voice support for the president.
Tanks were seen in the area and large numbers of residents joined the protests, residents said.
Demonstrators planned to spend the night in Change Square, an AFP correspondent said.
Signup to our newsletter and follow us on Facebook and Twitter!
The government voiced "profound regret" over the victims, and said it would launch an investigation aimed at punishing "those who provoked" the violence, in a statement published by the official Saba news agency.
Speaking not far from the scene of the violence, Saleh said he will travel to the United States in the coming days.
"Not for treatment, because I am well, but in order to create favourable conditions... for the presidential election," set for February 21, he told a news conference in Sanaa.
Saleh, who was wounded in a June 3 explosion at his Sanaa palace and then airlifted for treatment to Saudi Arabia, needs "important" treatment abroad, Jamal Benomar, the UN envoy in Yemen, said on Wednesday.
The national unity government, headed by the opposition, that is leading a three-month transition period before the February polls, on Saturday unveiled its programme, making clear the impoverished country needs urgent help.
"The government is going to try to convince its brother countries and friends to create a special international fund for Yemen," Prime Minister Mohammed Basindawa told parliament, Saba reported.
Many Yemenis face severe food shortages, months of political tension have devastated public services that were already weak, and government forces have not been able to stamp out an Al-Qaeda-linked insurgency in the restive south.
Last week, UN agencies said nearly four million Yemenis will be affected by the country's political and economic crisis in 2012, more than half of whom will suffer from acute food insecurity.
Basindawa said the new funds would be spent to ensure Yemenis had an adequate supply of oil, gas, water and electricity, but offered no specifics on where the money would come from.
He also pledged aid to the families of "martyrs" killed during the year of unrest.
But despite the political deal brokered by the Gulf Cooperation Council (GCC) that charts the path for Saleh's departure, the unrest has showed no signs of abating.
The tens of thousands who braved the streets of Sanaa and Taez to demand regime change have in part returned to denounce the GCC deal, demanding that Saleh and his allies be held accountable for their alleged crimes.