"Around dawn, the regime went crazy and started shelling hysterically," Homs-based activist Abu Rami told The Associated Press via Skype from rebel-held Old Homs. "An average of five rockets a minute are falling," he said, asking to be identified by his nickname for fear of reprisal. Most residents who still live in rebel-held areas around the city were hiding in shelters, he said.

Regime forces fired rockets and mortar shells at the rebel-held neighborhoods of Old Homs, Khaldiya, Qusour and Jouret el-Shayah, the activist said, adding that regime forces were also targeting villages around Homs and the rebel-held town of Rastan to the north.

In this image taken from video obtained from the Shaam News Network, which has been authenticated based on its contents and other AP reporting, smoke rises from houses due to government shelling in Homs, Syria, on Friday, Oct. 5, 2012. (AP Photo/Shaam News Network via AP video)

Earlier this week, Syrian refugees in Lebanon said their villages in Homs province had come under heavy air attack from so-called barrel bombs, makeshift weapons consisting of containers stuffed with explosives.

After weeks of stalemate in Aleppo, rebel fighters announced a new push last week to take the city, but the regime has fought back hard, shelling from tanks and bombing from the air.

An AP journalist in Aleppo said fighting has intensified this week, and that the rebels appear to be losing some ground in close-quarter combat.

Over a period of a few days, rebels lost control of several buildings in one of the front-line neighborhoods, Saif al-Dawla, he said.