Explosions shook several embattled Syrian cities on Sunday before polls opened for a vote on a new constitution that could keep President Bashar al-Assad in power until 2028.
Human rights campaigners reported blasts in Homs, Hama, Deir al-Zor, Deraa and some smaller towns caught up in an almost year-long uprising against four decades of Assad family rule.
Syrian television said voting had begun in the referendum on a constitution which Assad says will lead to a multi-party parliamentary election in three months, but which his opponents see as a sick joke given the violence convulsing the country.
"No one is going to vote," said activist Omar on Saturday from the rebel-held Baba Amro district of Homs, which Assad's forces have bombarded and besieged for more than three weeks.
"This was a constitution made to Bashar's tastes and meanwhile we are getting shelled and killed," he said. "More than 40 people were killed today and you want us to vote?"
The security forces killed at least 100 people, including six women and 10 children, across Syria on Saturday, the Syrian Network for Human Rights said in a statement.
The Syrian government, backed by Russia, China and Iran, and undeterred by Western and Arab pressure to halt the carnage, says it is fighting foreign-backed "armed terrorist groups".
Its onslaught on parts of Homs has created harrowing conditions for civilians and rebels.
A video posted by activists on YouTube showed Mohammad al-Mohammad, a doctor at a makeshift clinic in Baba Amro, holding a 15-year-old boy hit in the neck by shrapnel and spitting blood.
"It is late at night and Baba Amro is still being bombarded. We can do nothing for this boy," said the doctor, who has also been treating Western journalists wounded in the city.
American correspondent Marie Colvin and French photographer Remi Ochlik were killed in the bombardment of Homs last week and other Western journalists in the city were wounded. The group is still trapped there despite Red Cross efforts to extract them.
Red cross struggles for access
The International Committee of the Red Cross (ICRC) said it was still unable to evacuate distressed civilians from Baba Amro. After a day of talks with Syrian authorities and opposition fighters, it said there were "no concrete results".
"We continue our negotiations, hoping that tomorrow (Sunday) we will be able to enter Baba Amro to carry out our life-saving operations," spokesman Hicham Hassan said in Geneva.
Despite the violence in provincial cities across Syria, voting on the constitution went ahead in calmer areas.
If approved, it would drop an article making Assad's Baath party the leader of state and society, allow political pluralism and enact a presidential limit of two seven-year terms.
But the limit will not be enforced retrospectively, meaning that Assad, already in power for 11 years, could serve another two terms after his current one expires in 2014.
Dozens of people lined up to vote in two polling stations visited by a Reuters journalist in Damascus. "I've come to vote for President Bashar, God protect him and give him victory over his enemies," said Samah Turkmani, in his 50s.
Bassam Haddad, the director of one polling centre, said: "From the beginning the voting has been much better than we expected. We can say 200% above expectations."
Another voter, Majed Elias, said: "This is a national duty, whether I agree or not, I have to come and vote... I agree with the draft constitution, even if I object to some parts. Every Syrian must ride the wave of reform to achieve what he wants."
Anti-Assad activists have called for a boycott of a vote they see as meaningless. They said they would try to hold protests near polling stations in Damascus and suburbs where troops drove out insurgents last month.
Some said security forces had stopped people venturing out to buy food in Homs on Saturday, confiscated their Interior Ministry-issued identification cards and informed them the cards could be retrieved at specified polling centres the next day.
"They want to force people to vote in this doctored, so-called referendum," activist Mohammad al-Homsi said from Homs.
This is Syria's third referendum since Assad inherited power from his late father. The first installed him as president in 2000 with an official 97.29% 'yes' vote. The second renewed his term seven years later with 97.62% in favour.