Syrian activists sent Al Jazeera a list naming 70 people from across the country who they said had been killed by security forces during the "Great Friday" protests.
Map of April 22 'Great Friday' protests across Syria
Fifteen of the deaths took place in Izraa, near the flashpoint southern town of Daraa, according to the list.
Deaths were reported in Douma and Zamalka, near Damascus (see this video posted from an unknown source from Zamalka).
Other places where protesters were killed include Homs, Syria's third largest city, Moadamia and Daraa.
Demonstrators marching in peace were surprised by security forces' live ammunition, according to Hazem, a protester who spoke to Al Jazeera via phone from a Damascus suburb.
"Demonstrators were going with olive branches, it was peaceful" until they were "surprised by live ammunition from some security forces in one of the flats of the street", Hazem said.
The protesters took to the streets to mark what activists dubbed "Great Friday" - the biggest demonstrations against Bashar al-Assad's government to date.
Map of April 22 'Great Friday' protests across Syria
Al Jazeera's Rula Amin reported from Damascus, which until now had been relatively calm, that the level of tension in the city on Friday marked a new point in the uprising.
"This day is turning into a very bloody day, probably the bloodiest since the protests started," she said.
A heavy security presence prevented protests from taking off in Damascus.
"Obviously the government want[s] to make a point, the capital is a redline and they will not allow the protests to reach the capital," she said.
Several witnesses, including medical professionals, told Al Jazeera that many of the injured were either being refused access to hospitals or were too scared to seek treatment.
A spokesperson for the ministry of information told Al Jazeera on Friday that security forces would fire on protesters only if they were fired upon first.
State television, meanwhile, aired a talk show where speakers blamed foreign media, including Al Jazeera, Al Arabiya and BBC Arabic, for inciting the protests.
Violence in Homs
Speaking under condition of anonymity, a witness in Homs described how about 200 protesters, moving ahead of a 3,000-strong group, came under fire as they marched down Cairo Street, close to the Clock Square that has been the city's focus for protests.
"Suddenly the security opened fire on us randomly," the activist told Al Jazeera by phone.
One of those killed in the city by government officers was a 25-year-old protester named Mohammed Bassam al-Kahil, he said.
Meanwhile, another witness in Hasakah, in Syria's mainly Kurdish northeast, told Al Jazeera that demonstrators gathering at a mosque after prayers were attacked by pro-government protesters.
Syrian activists co-ordinating the protests against al-Assad's rule have demanded the abolition of his Baath Party's monopoly on power and the establishment of a democratic political system.
In the first joint statement since protests erupted five weeks ago, the Local Co-ordination Committees, representing provinces across Syria, said "freedom and dignity slogans cannot be achieved except through peaceful democratic change".
"All prisoners of conscience must be freed. The existing security apparatus has to be dismantled and replaced by one with specific jurisdiction and which operates according to law," the joint statement said.
Contest of wills
On the eve of the protests, witnesses said security forces were setting up checkpoints in areas surrounding Damascus, checking people's ID cards.
The demonstrations are a test of whether Assad's decision to lift emergency law, imposed by his Baath Party when it took power in a coup 48 years ago, will defuse mass discontent with repression and corruption.
A spokeswoman for Syria's information ministry says security forces could open fire if protesters shoot first
Haitham Maleh, who heads the Syrian Human Rights Association, a civil-rights group, told Al Jazeera that the regime's reforms only went a fraction of the way towards satisfying the protesters' demands for more freedom, democracy and the legalisation of opposition parties.
"The government will not do anything, I think, and the strikes will get bigger and bigger," he said.
Al Jazeera's Amin said that because one of the conditions for the newly gained right to protest was to request a permit, today's protests fell outside of the changes.
"There was no time for anyone to ask for permission for today," she said.
Aided by his family and a pervasive security apparatus, Assad, 45, has absolute power in Syria.
More than 220 protesters have been killed since pro-democracy protests erupted on March 18 in Daraa, rights campaigners say.
A decree Assad signed on Thursday that lifted emergency law is seen by the opposition as little more than symbolic, since other laws still give entrenched security forces wide powers.
Robert Fisk, the Middle East reporter, analyses the Syrian uprising in interview to Al Jazeera
The authorities have blamed armed groups, infiltrators and Sunni Muslim armed groups for provoking violence at demonstrations by firing on civilians and security forces.
Commenting on the Syrian situation, Robert Fisk, the veteran Middle East reporter for the UK's Independent newspaper, says Assad appears to be "stepping backwards" .
"Once you start giving these concessions, the crowds on the streets want more and it will always end at the same demand: end of the dictator," he told Al Jazeera from the Lebanese capital Beirut on Friday.
With his belated concessions, Assad is "is now enduring the failures that he committed 11 years ago", Fisk said.
While crowds in Damascus and Deraa are getting bigger, he said Assad will not be fleeing Syria yet.
"He's in a lot of trouble and there must be a lot of talk in the presidential palace tonight," he said.
Washington urged Syria to stop the violence against protesters and William Hague, the British foreign secretary, said emergency law should be "lifted in practice not just in word".
Western and other Arab countries have mostly muted their criticism of the killings in Syria for fear of destabilising the country, which plays a strategic role in many of the conflicts in the Middle East.
Syria is technically at war with Israel but has kept its Golan Heights front quiet since a 1974 ceasefire.