The opposition Local Coordination Committees of Syria said at least 23 people were killed in the first helicopter attacks of the growing conflict, CNN reported.
A government blockade and water and electricity outages in Homs were crippling the opposition stronghold, CNN said.
Opposition activists said 23 people were killed Tuesday when Syrian troops ambushed a group trying to smuggle Western journalists out of the country.
Survivors of Tuesday's attack said government troops moved in as the group tried to make its way to Lebanon, leaving 23 of the 50 dead, CNN said.
British photographer Paul Conroy, who was wounded in an attack on the Homs neighborhood of Baba Amr, was one the people who made it across the border to Lebanon. Some of the group was forced to turn back toward Homs, however, including Spanish journalist Javier Espinoza, CNN said.
The Sunday Times of London confirmed Conroy was "in good shape and good spirits."
There was no word if the bodies of Sunday Times reporter Marie Colvin and French photographer Remi Ochlik, killed by Syrian artillery fire last week, were recovered.
The Local Coordination Committees of Syria said wounded Le Figaro reporter Edith Bouvier remained in Homs. The activist group said Bouvier has demanded guarantees from the Syrian government that she could keep her photos and recordings.
A 13-year-old boy was killed by sniper fire Wednesday in the eastern city of Deir Ezzor, the Syrian Observatory for Human Rights said. Deaths from rocket fire were also reported in the western city of Rastan.
Thousands of civilians have been killed in the Syrian government's crackdown against a pro-democracy uprising that began last March, and the violence has been intensifying in recent weeks, U.N. officials said.
The United Nations said the death toll in Syria's ongoing political crisis exceeds 100 civilians a day, including women and children.
Valerie Amos, head of U.N. relief operations, said Wednesday she was "deeply disappointed" her repeated requests to visit Syria to assess the humanitarian situation have been denied.
"Given the rapidly deteriorating humanitarian situation, with an increasing need for medical assistance, food and basic supplies, improving access so that assistance can reach those in urgent need is a matter of the highest priority," Amos said. "Every day that we are not able to reach people, especially in the towns where there is heavy fighting, prolongs their suffering."
CNN said reports from Syria suggest government forces are killing citizens in an attempt to eliminate opponents seeking the removal of President Bashar Assad.
U.N. Human Rights Commissioner Navi Pillay Tuesday called for an immediate humanitarian cease-fire to end the fighting and assist civilians.