(CBS/AP) BEIRUT -- A suicide car bomb exploded Saturday in a southern Syrian city known as the birthplace of the country's uprising, and casualties were reported, the state-run news agency said.
The blast came as Syria continued to block a Red Cross convoy from delivering badly needed aid to a rebellious neighborhood in the central city of Homs, and as anti-regime activists said government shelling of Homs had resumed.
The SANA news agency said the suicide bombing occurred at a roundabout in the heart of Daraa, an area known as Daraa al-Balad, causing multiple casualties and damaging buildings and shops there.
The British-based Syrian Observatory for Human Rights said at least two people were killed and several others wounded in the explosion.
Syria has seen a string of suicide bombings, the last on Feb. 10, when twin suicide bombs struck security compounds in the government stronghold city of Aleppo, killing 28 people and bringing significant violence for the first time to the city.
The capital, Damascus, another stronghold of President Bashar Assad, has seen three suicide bombings in the past two months.
The regime has touted the attacks as proof that it is being targeted by "terrorists." The opposition accuses forces loyal to the government of being behind the bombings to tarnish the uprising.
Saturday's bombing in Daraa marked the first time a suicide bombing struck an opposition stronghold. Daraa is the birthplace of the nearly year-old uprising against Assad. The revolt has killed more than 7,500 people, according to most recent U.N. estimates.
Elsewhere, Syrian troops shelled Saturday several districts in the rebellious central city of Homs, where a standoff continued between a Red Cross convoy and the government that has blocked the delivery of food, medical supplies and blankets to the thousands still stranded in the area.
Abu Hassan al-Homsi, a doctor at a makeshift clinic in Khaldiyeh district of Homs, said he treated a dozen wounded.
"This has become routine, the mortars start falling early in the morning," he said. Several homes were damaged from the morning shelling, which he described as steady but intermittent. Most of those he treated were lightly wounded, al-Homsi added.
The Local Coordination Committees activist network said mortars slammed into Khaldiyeh, Bab Sbaa and Khader districts of the city early Saturday.
In addition, shells fell Saturday on Homs' Jobar residential neighborhood, where thousands of civilians from an area overrun by government troops had taken refuge, reports Reuters, citing an opposition activist group.
Humanitarian conditions in Baba Amr, a western neighborhood of Homs that was overran by troops on Thursday, have been described as catastrophic, with extended power outages, shortages of food and water, and no medical care for the sick and wounded.
Syrian government forces took control of the neighborhood after rebels fled the district under constant bombardment that activists said killed hundreds of people since early February. The Syrian regime has said it was fighting "armed gangs" in Baba Amr, and had vowed to "cleanse" the neighborhood.
"It is unacceptable that people who have been in need of emergency assistance for weeks have still not received any help," said Jakob Kellenberger, president of the International Committee of the Red Cross.
The Red Cross said it had received permission from the government of President Bashar Assad on Thursday to enter Baba Amr, on the western side of Homs. A convoy of seven trucks with 15 tons of humanitarian aid left Damascus on Friday, taking several hours in heavy snowfall to reach Homs.
Once in Homs, it was poised to enter Baba Amr but authorities then blocked their access, the Red Cross said. There was no explanation from the government about the change.
"We are staying in Homs tonight in the hope of entering Baba Amr in the very near future," Kellenberger said Friday night.
U.N. Secretary-General Ban Ki-moon called on Syria to give humanitarian workers immediate access to people who desperately need aid.
"The images which we have seen in Syria are atrocious," said Ban. "It's totally unacceptable, intolerable. How, as a human being, can you bear this situation?"