Syrian government forces killed 31 people around the country on Friday, including 10 demonstrators hit by mortar rounds in Homs, a centre of opposition to President Bashar al-Assad's rule, activists said.
Mortar rounds hit a demonstration in the district of Bab Houd, said Homs-based opposition activist Abu Imad, who added that the al-Hanableh mosque in Bab Dreib had also been hit as worshippers were leaving after Friday Muslim prayers.
Walid Fares, an activist in the Khalidiya district of Homs, said four protests were under way in different parts of the city, and that he had received reports that all had been hit by mortar fire.
He said he had also heard mortar rounds landing in his neighbourhood since early in the morning.
The resumption of heavy shelling followed a few days of relative calm during which U.N. humanitarian chief Valerie Amos visited Homs and said part of the city had been completely destroyed.
The Baba Amr district was besieged and shelled for a month before rebels fled and government troops moved in.
Thirty tanks entered my neighbourhood at 7 a.m. this morning and they are using their cannons to fire on houses, said Karam Abu Rabea, a resident of the Karm al-Zeitoun district in Homs.
There is gunfire and they are using rocket-propelled grenades, he said, adding that the streets had emptied in his district and people were taking refuge in their homes.
The grassroots Local Coordination Committees said nine people had been killed in the city of Homs, three in Homs province, two in Idlib and two in Damascus.
The UK-based Syrian Observatory for Human Rights said security forces had killed two people in house-to-house raids near the Turkish border and three in Hama city.
Around the country, Assad's opponents have flooded onto the streets, in many cases after Friday prayers, to demonstrate against his autocratic rule, and activists reported that security forces had fired on the protesters.
Humanitarian chief Amos said on Thursday she had asked the Syrian government to allow access for humanitarian aid to be given to victims of the turmoil.
U.N.-Arab League envoy Kofi Annan is due to arrive in Damascus on Saturday to try to calm the year-old conflict which threatens to turn into civil war.
(Additional reporting by Khaled Yacoub Oweis in Amman, editing by Tim Pearce)