The violence comes as President Bashar Assad's regime is becoming increasingly isolated over its bloody crackdown on dissent. Five European countries and six Arab Gulf nations have pulled their ambassadors out of Damascus, and the US has closed its embassy in Syria. Germany, whose whose envoy Syria this month, also said he would not be replaced.
But Assad was bolstered Tuesday by a visit from Russia's Foreign Minister Sergey Sergey Lavrov and the country's intelligence chief, Mikhail Fradkov. In the talks in Damascus, the Russians pushed for a solution to the Syrian crisis that would include reforms by the regime and a dialogue with the opposition - but not for Assad to step down.
During the meeting, Assad said Syria is determined to hold a national dialogue with the opposition and independent figures, saying his government was "ready to cooperate with any effort that boosts stability in Syria," according to the Syrian state news agency SANA.
The Syrian opposition rejects any talks with the regime and says they accept nothing less than Assad's departure.
On Saturday, Russia and China blocked a Western- and Arab-backed UN Security Council resolution supporting calls for Assad to hand over some powers as a way to defuse the 11-month-old crisis.
The Britain-based Syrian Observatory for Human Rights said at least 50 people were killed in Wednesday's shelling of the Homs neighborhoods of Bayadah, Baba Amr, Khaldiyeh and Karm el-Zeytoun. The group also said that 23 homes were heavily damaged in Baba Amr alone.
Omar Shaker, an activist in Baba Amr, said his neighborhood was under "very intense shelling" by tanks, mortars, artilleries and heavy machine guns. Shaker added that he counted five bodies Wednesday in his district.
"The situation is dire. We are short of food, water and medical aid. Doctors have collapsed after treating the wounded without rest for five days," Shaker said. "We want Lavrov to come and spend a night in Homs to see what we have been passing through."
The activist urged the international community to set up a safe passage so that women and children can leave volatile areas of Homs. The head of the Observatory, Rami Abdul-Rahman, said the regime was trying "exhaust rebels in preparation for storming neighborhoods."
The Observatory and another activist group, the Local Coordination Committees, also reported intense clashes between troops loyal to Assad and defectors on Wednesday in the province of Idlib, bordering Turkey. The Observatory said at least five soldiers were killed in the clashes.
The UN estimates the government crackdown has killed more than 5,400 people since March, making Syria's conflict one of the deadliest of the Arab Spring.
Hundreds more are believed to have died since the U.N. released that figure in January, but the chaos in the country has made it impossible for the world body to update its figures.